Tag Archives: poliovirus

John Enders: “The Father of Modern Vaccines”

John Enders (1897- 1985) was one of the subjects of a recent posting, Vaccine Research Using Children (1). In the 1950s, Enders used severely handicapped children at the Walter E. Fernald State School in Massachusetts to test his measles vaccine—a vaccine that may have saved well over 100 million lives. Irrespective of the ethical issues raised by the incident at the Fernald School, Nobel laureate John Enders was one of the most highly renowned of virologists, and there is much more to his story, some of which is told here.

John F. Enders, November 17, 1961
John F. Enders, November 17, 1961

Enders grew up in West Hartford, Connecticut. His father, who was CEO of the Hartford National Bank, left the Enders family a fortune of $19 million when he passed away. Thus, John Enders became financially independent, which may help to account for his rather atypical path to a career in biomedical research.

Enders was under no pressure to decide on a vocation, and had no particular objective in mind when he enrolled at Yale University in 1915. In 1917 (during the First World War) he interrupted his Yale studies to enlist in the Naval Reserve. He became a Navy pilot and then a flight instructor. After three years of naval service, Enders returned to Yale to complete his undergraduate studies.

After Enders graduated from Yale he tried his hand at selling real estate in Hartford. However, selling real estate troubled him, in part because he believed that people ought to know whether or not they wanted to buy a house, rather than needing to be sold (2, 3). Thus, Enders considered other callings, finally deciding to prepare for a career teaching English literature.

What might have motivated that particular choice? Here is one possibility. During the years when Enders was growing up in West Hartford, his father handled the financial affairs of several celebrated New England writers, including Mark Twain. [The young Enders always admired Twain’s immaculate white suits whenever he visited the Enders home (3).] So, perhaps Enders’ early exposure to eminent writers among his father’s clients planted the seed for his interest in literature. In any case, Enders enrolled at Harvard to pursue graduate studies in preparation for his new calling.

Enders received his M.A. degree in English Literature from Harvard in 1922. Moreover, he was making substantial progress towards his Ph.D., when his career took yet another rather dramatic turn; one reminiscent of that taken later by Harold Varmus, who likewise did graduate studies in English literature at Harvard, with the intent of becoming an English teacher (4).

The changes in the career plans of both Enders and Varmus—from teaching English literature to biomedical research—were prompted by the friends each had who were at Harvard Medical School. Varmus’ friends were his former classmates from Amherst College. Enders first met his friends from among his fellow boarders at his Brookline rooming house.

Dr. Hugh Ward, an instructor in Harvard’s Department of Bacteriology and Immunology, was one of the friends Enders met at his rooming house. Enders wrote, “We soon became friends, and thus I fell into the habit of going to the laboratory with him in the evening and watching him work (5).” Enders was singularly impressed by Ward’s enthusiasm for his research (5).

During one of the trips that Ward and Enders made to the laboratory, Ward introduced Enders to Hans Zinsser, Head of Harvard’s Department of Bacteriology and Immunology. Zinsser was an eminent microbiologist, best known for isolating the typhus bacterium and for developing a vaccine against it.

Enders soon became fascinated by the research in Zinsser’s lab. So, at 30-years-of-age, and on the verge of completing his Ph.D. in English Literature, Enders changed career plans once again; this time to begin studies toward a doctorate in bacteriology and immunology, under Zinsser’s mentorship.

Zinsser, a distinguished microbiologist, was also a sufficiently accomplished poet to have some of his verses published in The Atlantic Monthly. That aspect of Zinsser likely impressed the literate Enders, who described his mentor as: “A man of superlative energy. Literature, politics, history, and science-all he discussed with spontaneity and without self-consciousness. Everything was illuminated by an apt allusion drawn from the most diverse sources, or by a witty tale. Voltaire seemed just around the corner, and Laurence Sterne upon the stair. . . . Under such influences, the laboratory became much more than a place just to work and teach; it became a way of life (3).”

Enders was awarded his Ph.D. in Bacteriology and Immunology in 1930. Afterwards, he remained at Harvard, as a member of the teaching staff, until 1946, when he established his own laboratory at the Children’s Medical Center in Boston.

Why might Enders have been satisfied staying so long at Harvard, for the most part as Zinsser’s underling? Perhaps that too might be explained by his financial independence. In any case, in 1939, while Enders was still at Harvard, he initiated the singularly significant course of research for which he is best remembered.

In 1939, in collaboration with Dr. Alto Feller and Thomas Weller (then a senior medical student), Enders began to develop procedures to propagate vaccinia virus in cell culture. After achieving that goal, the Enders team applied their cell culture procedures to propagate other viruses, including influenza and mumps viruses.

Enders and his coworkers were not the first researchers to grow viruses in cell culture. However, they were the first to do so consistently and routinely. Thus, the Enders lab launched the “modern” era of virus research in vitro. Virology could now advance much more quickly than before, since most virologists would no longer need to grow, or study their viruses only in live animals.

A recurrent theme on the blog is that key scientific discoveries may well be serendipitous. The case in point here was the unforeseen 1949 discovery by Enders and his young collaborators, Tom Weller and Frederick Robbins, that poliovirus could be grown in cultured cells. That crucial discovery made it possible for Jonas Salk and Albert Sabin to generate a virtually unlimited amount of poliovirus and, thus, to create their polio vaccines. Importantly, the discovery happened at a time when polio researchers believed that poliovirus could grow only in nerve cells. Their dilemma was that nerve cells could not be cultured in the laboratory.

Enders, Weller, and Robbins were not working on polio, nor did they have any immediate intention of working on polio when they made their finding. In fact, when the thirty-year-old Robbins (see Aside 1) came to work with Enders, he proclaimed that he wanted to work on any virus, except polio (6).

[Aside 1: Weller was one year older than Robbins. Both had been Army bacteriologists during the Second World War, and they were classmates and roommates at Harvard Medical School when they came to Enders for research experience. Robbins’ father-in-law, John Northrop, shared the 1946 Nobel Prize in chemistry with James Sumner and Wendell Stanley (7). In 1954, Robbins joined his father-in-law as a Nobel laureate (see below).]

The Enders team was trying to grow varicella (the chicken pox virus) when, on a whim; they made their critical discovery. It happened as follows. While attempting to propagate varicella virus in a mixed culture of human embryonic skin and muscle cells, they happened to have some extra flasks of the cell cultures at hand. And, since they also had a sample of poliovirus nearby in their lab storage cabinet; they just happened to inoculate the extra cell cultures with polio virus.

The poliovirus-infected cultures were incubated for twenty days, with three changes of media. Then, Enders, Weller, and Robbins asked whether highly diluted extracts of the cultures might induce paralysis in their test mice. When those highly diluted extracts indeed caused paralysis in the mice, they knew that poliovirus had grown in the cultures. See Aside 2.

[Aside 2: Whereas Enders, Weller, and Robbins did not have pressing plans to test whether poliovirus might grow in non-neuronal cells, they probably were aware of already available evidence that poliovirus might not be strictly neurotropic. For instance, large amounts of poliovirus had been found in the gastrointestinal tract.]

Despite the exceptional significance of their discovery, Robbins said, “It was all very simple (6).” Weller referred to the discovery as a “fortuitous circumstance (6).” Enders said, “I guess we were foolish (6)”—rather modest words from a scholar of language and literature. See Aside 3.

[Aside 3: Current researchers and students might note that Enders’ entire research budget amounted to a grand total of two hundred dollars per year! The lab did not have a technician, and Weller and Robbins spent much of their time preparing cells, media, and reagents, as well as washing, plugging, and sterilizing their glassware.]

In 1954, Enders, Weller, and Robbins were awarded the Nobel Prize for Physiology or Medicine for their polio discovery. Interestingly, they were the only polio researchers to receive the Nobel award. The more famous Salk and Sabin never received that honor (8).

If Enders were so inclined, might he have produced a polio vaccine before Salk and Sabin? Weller and Robbins wanted to pursue the vaccine project, and Enders agreed that they had the means to do so. In fact, Weller actually had generated attenuated poliovirus strains by long-term propagation of the virus in culture; a first step in the development of a vaccine (3). Yet for reasons that are not clear, Enders counseled his enthusiastic young colleagues to resist the temptation (6). See Aside 4.

[Aside 4: Enders may have spared Weller and Robbins the sort of anguish that Salk experienced when some of his killed vaccine lots, which contained incompletely inactivated poliovirus, caused paralytic poliomyelitis in some 260 children (8).]

The Enders poliovirus group began to disperse, beginning in 1952 when Robbins became a professor of pediatrics at Western Reserve. Weller left in 1954 to become chairman of the Department of Tropical Public Health at Harvard.

Regardless of whether Enders might have regretted not pursuing the polio vaccine, he soon would play a hands-on role in the development of the measles vaccine. The first critical step in that project occurred in1954, at the time when the Salk polio vaccine was undergoing field trials. It was then that Enders and a new young coworker, pediatric resident Thomas Peebles (Aside 5), succeeded in cultivating measles virus in cell culture for the first time.

[Aside 5: Enders was known for nurturing bright young investigators. His latest protégé, Tom Peebles, spent four years in the Navy, as a pilot, before enrolling at Harvard Medical School. Peebles graduated from medical school in 1951, and then did an internship at Mass General, before coming to the Enders lab to do research on infectious diseases in children. When Enders suggested to Peebles that he might try working on measles, Peebles eagerly accepted.]

Here is a piece of the measles vaccine story that happened before Peebles’ success growing the virus in cell culture. At the very start of the vaccine project, Enders and Peebles were stymied in their attempts to get hold of a sample of measles virus to work with. Their quest for the virus began with Peebles searching the Enders laboratory freezers for a sample. Finding none there, Peebles next inquired at Boston area health centers; still without success. After several more months of fruitless searching, Peebles received an unexpected phone call from the school physician at the Fay School (a private boarding school for Boys in a Boston suburb), telling him about a measles outbreak at the school. Peebles immediately rushed to the school, where he took throat swabs, as well as blood and stool samples from several of the school’s young patients. He then rushed back to the Enders laboratory, where he immediately inoculated human infant kidney cells with his samples. [Enders obtained the cells from a pediatric neurosurgeon colleague, who treated hydrocephalus in infants by excising a kidney, and shunting cerebrospinal fluid directly to the urethra.]

Peebles monitored the inoculated kidney cell cultures for the next several weeks, hoping for a sign of a virus replicating in them. Seeing no such indication of a virus in the cultures, Peebles made a second trip to the Fay School, which, like the first trip, was unproductive.

On a third trip to the school, Peebles obtained a sample from an 11-year-old boy, David Edmonston. The sample from young Edmonston indeed seemed to affect the kidney cell cultures. Still, Peebles needed to carry out several additional experiments before he could convince a skeptical Enders and Weller—first, that a virus had replicated in the cultures and, second, that it was measles. Peebles convinced the two doubters by demonstrating that serum from each of twelve convalescing measles patients prevented the virus from causing cytopathic effects in the inoculated cell cultures. That is, the convalescent serum neutralized the virus. The measles virus growing in those cultures was named for its source. It is the now famous Edmonston strain.

Enders, in collaboration with Drs.Milan Milovanovic and Anna Mitus, next showed that the Edmonston strain could be propagated in chick embryos (3). Then, working with Dr. Samuel Katz (1), Enders showed that the egg-adapted virus could be propagated in chicken cell cultures.

By 1958, Enders, Katz, and Dr. Donald Medearis showed that the Edmonston measles virus could be attenuated by propagating it in chicken cells. Moreover, the attenuated virus produced immunity in monkeys, while not causing disease (3). Thus, the attenuated Edmonston strain became the first measles vaccine. [Tests of the vaccine in humans led to the episode at the Fernald School (1).]

The Enders measles vaccine was attenuated further by Maurice Hilleman at Merck (9). In 1971 it was incorporated into the Merck MMR combination vaccine against measles, mumps, and rubella (9, 10).

The MMR vaccine has had a remarkable safety record, and it was widely accepted until 1997; the time when the now discredited claim that the vaccine is linked to autism first emerged (10). However, even prior to the MMR/autism controversy, vaccine non-compliance was already a problem. But, in that earlier time, parents were declining to have their children vaccinated, not because of safety issues, but rather because they questioned the severity of measles. Ironically, that was why David Edmonston refused to have his own son receive the vaccine.

Despite receiving the Nobel Prize for his polio work, Enders maintained that developing the measles vaccine was more personally satisfying to him and more socially significant (3).

References:

  1. Vaccine Research Using Children, Posted on the blog July 7, 2016.
  2. John F. Enders-Biographical, The Nobel Prize in Physiology or Medicine 1954. From Nobel Lectures, Physiology or Medicine 1942-1962, Elsevier Publishing Company, Amsterdam, 1964.
  3. Weller TH, Robbins FC, John Franklin Enders 1897-1995, A Biographical Memoir www.nasonline.org/publications/…/endersjohn.pdf [An excellent review of Enders’ life and career.]
  4. Harold Varmus: From English Literature Major to Nobel Prize-Winning Cancer Researcher, Posted on the blog January 5, 2016.
  5. John F. Enders, “Personal recollections of Dr. Hugh Ward,” Australian Journal of Experimental Biology 41:(1963):381-84. [This is the source of the quotation in the text. I found it in reference 3.]
  6. Greer Williams, Virus Hunters, Alfred A. Knopf, 1960.
  7. Wendell Stanley: First to Crystallize a Virus, Posted on the blog April 23, 2015.
  8. .Jonas Salk and Albert Sabin: One of the Great Rivalries of Medical Science, Posed on the blog March 27, 2014.
  9.  Maurice Hilleman: Unsung Giant of Vaccinology, Posted on the blog April 24, 2014.
  10.  Andrew Wakefield and the Measles Vaccine Controversy, Posted on the blog February 9, 2015.

 

C.I.A. Vaccine Ruse

In the March 27, 2014 posting, Jonas Salk and Albert Sabin: One of the Great Rivalries of Medical Science, I wrote the following:

“Several polio hotspots remain in the world. Three major ones are Pakistan, Afghanistan, and Nigeria. Recent outbreaks have also occurred in Syria and Somalia. In each of these instances, social and political climates make it difficult to carry out eradication campaigns…As recently as March 2014, militants attacked a polio vaccination team in northwest Pakistan, detonating a roadside bomb and then opening fire on their convoy, killing 12 of their security team, and wounding dozens more. Some Pakistani religious leaders denounced the vaccination campaign in Pakistan as a cover for spying …”

The article by Mark Mazzetti in yesterday’s (May 20, 2014) New York Times, entitled: U.S. Cites End to C.I.A. Ruses Using Vaccines, reaffirms that accusations by the Taliban and Pakistani clerics were not simply propaganda or paranoia. Mazzetti’s piece is as follows:

“WASHINGTON — Three years after the Central Intelligence Agency set up a phony hepatitis vaccination program in Pakistan as part of the hunt for Osama bin Laden, the Obama administration told a group of American health educators last week that the agency no longer uses immunization programs as a cover for spying operations.

In a letter to leaders at a dozen schools of public health, President Obama’s senior counterterrorism adviser said the C.I.A. had banned the practice of making “operational use” of vaccination programs, adding that the agency would not seek to “obtain or exploit DNA or other genetic material acquired through such programs.”

The letter from the adviser, Lisa O. Monaco, comes more than a year after public health officials wrote to Mr. Obama expressing anger that the United States had used immunization programs as a front for espionage. The educators were protesting the C.I.A.’s employment of a Pakistani doctor, Shakil Afridi, to set up a hepatitis B vaccination program in Abbottabad to gain access to a compound where Bin Laden was believed to be hiding.

“While political and security agendas may by necessity induce collateral damage, we as a society set boundaries on these damages, and we believe this sham vaccination campaign exceeded those damages,” the educators’ letter said.

The intelligence operation failed to determine whether Bin Laden was in the compound. The Qaeda leader was killed shortly afterward, in May 2011, in a nighttime raid carried out by Navy SEALs. Dr. Afridi was arrested days after the raid and remains in jail in Pakistan.

While in custody, Dr. Afridi told interrogators that he was introduced to C.I.A. officers in Pakistan by an employee of Save the Children. Both the C.I.A. and Save the Children have denied the aid group was used for spying, but the revelation led it to close its operations in Pakistan.

Since the C.I.A.’s vaccination program became public, dozens of public health workers in Pakistan have been killed, with militant groups sometimes announcing that the workers had been suspected of being spies.

John O. Brennan, the agency’s director, put the new policy into effect last August, an agency spokesman said. “By publicizing this policy,” said Ned Price, the spokesman, “our objective is to dispel one canard that militant groups have used as justification for cowardly attacks against vaccination providers.”

The earlier article, by Saeed Shah, in the July 11, 2011 The Guardian, entitled CIA Organised Fake Vaccination Drive to get Osama Bin Laden’s Family DNA, provides additional details.

“The CIA organised a fake vaccination programme in the town where it believed Osama bin Laden was hiding in an elaborate attempt to obtain DNA from the fugitive al-Qaida leader’s family, a Guardian investigation has found.

As part of extensive preparations for the raid that killed Bin Laden in May, CIA agents recruited a senior Pakistani doctor to organise the vaccine drive in Abbottabad, even starting the “project” in a poorer part of town to make it look more authentic, according to Pakistani and US officials and local residents.

The doctor, Shakil Afridi, has since been arrested by the Inter-Services Intelligence agency (ISI) for co-operating with American intelligence agents.

Relations between Washington and Islamabad, already severely strained by the Bin Laden operation, have deteriorated considerably since then. The doctor’s arrest has exacerbated these tensions. The US is understood to be concerned for the doctor’s safety, and is thought to have intervened on his behalf.

The vaccination plan was conceived after American intelligence officers tracked an al-Qaida courier, known as Abu Ahmad al-Kuwaiti, to what turned out to be Bin Laden’s Abbottabad compound last summer. The agency monitored the compound by satellite and surveillance from a local CIA safe house in Abbottabad, but wanted confirmation that Bin Laden was there before mounting a risky operation inside another country.

DNA from any of the Bin Laden children in the compound could be compared with a sample from his sister, who died in Boston in 2010, to provide evidence that the family was present.

So agents approached Afridi, the health official in charge of Khyber, part of the tribal area that runs along the Afghan border.

The doctor went to Abbottabad in March, saying he had procured funds to give free vaccinations for hepatitis B. Bypassing the management of the Abbottabad health services, he paid generous sums to low-ranking local government health workers, who took part in the operation without knowing about the connection to Bin Laden. Health visitors in the area were among the few people who had gained access to the Bin Laden compound in the past, administering polio drops to some of the children.

Afridi had posters for the vaccination programme put up around Abbottabad, featuring a vaccine made by Amson, a medicine manufacturer based on the outskirts of Islamabad.

In March health workers administered the vaccine in a poor neighbourhood on the edge of Abbottabad called Nawa Sher. The hepatitis B vaccine is usually given in three doses, the second a month after the first. But in April, instead of administering the second dose in Nawa Sher, the doctor returned to Abbottabad and moved the nurses on to Bilal Town, the suburb where Bin Laden lived.

It is not known exactly how the doctor hoped to get DNA from the vaccinations, although nurses could have been trained to withdraw some blood in the needle after administrating the drug.

“The whole thing was totally irregular,” said one Pakistani official. “Bilal Town is a well-to-do area. Why would you choose that place to give free vaccines? And what is the official surgeon of Khyber doing working in Abbottabad?”

A nurse known as Bakhto, whose full name is Mukhtar Bibi, managed to gain entry to the Bin Laden compound to administer the vaccines. According to several sources, the doctor, who waited outside, told her to take in a handbag that was fitted with an electronic device. It is not clear what the device was, or whether she left it behind. It is also not known whether the CIA managed to obtain any Bin Laden DNA, although one source suggested the operation did not succeed.

Mukhtar Bibi, who was unaware of the real purpose of the vaccination campaign, would not comment on the programme.

Pakistani intelligence became aware of the doctor’s activities during the investigation into the US raid in which Bin Laden was killed on the top floor of the Abbottabad house. Islamabad refused to comment officially on Afridi’s arrest, but one senior official said: “Wouldn’t any country detain people for working for a foreign spy service?”

The doctor is one of several people suspected of helping the CIA to have been arrested by the ISI, but he is thought to be the only one still in custody.

Pakistan is furious over being kept in the dark about the raid, and the US is angry that the Pakistani investigation appears more focused on finding out how the CIA was able to track down the al-Qaida leader than on how Bin Laden was able to live in Abbottabad for five years.

Over the weekend, relations were pummelled further when the US announced that it would cut $800m (£500m) worth of military aid as punishment for Pakistan’s perceived lack of co-operation in the anti-terror fight. William Daley, the White House chief of staff, went on US television on Sunday to say: “Obviously, there’s still a lot of pain that the political system in Pakistan is feeling by virtue of the raid that we did to get Osama bin Laden, something the president felt strongly about and we have no regrets over.”

The CIA refused to comment on the vaccination plot.”

National Public Radio’s Jason Beaubien filed the following for last night’s edition of All Things Considered:

“‘The CIA is not exclusively responsible for the problems we have in getting children vaccinated but it certainly didn’t make it anything easier,’ says Anthony Robbins, the co-editor of the Journal of Public Health Policy. Robbins wrote an editorial denouncing the CIA use of fake vaccination programs back in August of 2012. Even before bin Laden was killed in 2011, the Taliban had banned polio immunization in the parts of Pakistan it controls. The Taliban claimed the polio drops sterilize Pakistani children and vaccinators were American spies.

“The head of one large anti-polio campaign in Pakistan wasn’t happy to hear the CIA’s latest declaration. ‘I don’t think this statement is going to help in anyway,’ says Aziz Memon, who heads Rotary International’s polio eradication effort in Pakistan. He says Pakistanis were starting to forget about the controversy over the fake CIA vaccination campaign and now he expects the issue to blow up in the local media all over again.”

 

Jonas Salk and Albert Sabin: One of the Great Rivalries of Medical Science

Paralytic poliomyelitis was one of the world’s most feared diseases during the first half of the 20th century. However, the dread of poliovirus ended abruptly with the advent of the poliovirus vaccines in the 1950s. This posting tells the stories of the key players in the race to develop a polio vaccine. In particular, it features the rivalry between Jonas Salk and Albert Sabin, the two main contenders in the pursuit. While their vaccines together have led to the near disappearance of poliovirus worldwide, neither was recognized by the Nobel committee for his achievement. We begin with some background.

Poliovirus has long been especially interesting to me, both as a virologist and personally as well. The reason is that I was a child and young teenager during the annual polio epidemics of the 1940s and early 1950s, and can vividly remember the panic that set in early every summer of the pre-vaccine days, when the first neighbor or schoolmate was stricken. You were kept home from school and couldn’t even play outside. A visit to a hospital in those times was associated with the pitiful sight of young polio victims in the iron lungs that filled the wards, and even the hallways of hospitals back then.

iron lung

Not even the emergence of AIDS in the early 1980s evoked fear comparable to that brought on by poliomyelitis. Yet despite the dread of poliomyelitis, the disease actually struck many fewer victims than was commonly perceived by the public. The number of poliomyelitis cases in the United States was typically 20,000 to 30,000 per year in the 1940s and 1950s, while influenza still typically kills 40,000 to 50,000 Americans annually. Yet most individuals, then and now seem indifferent to influenza. What’s more, even the 1918 “Spanish Flu” epidemic, which was arguably the most devastating epidemic in human history, did not cause any panic, despite the fact that during the single month of October 1918, it killed 196,000 people in the United States alone! Estimates of the total number killed worldwide by the 1918 Spanish Flu range between 20 million and 50 million.

So, how can we explain the terror brought on by poliomyelitis? It wasn’t simply because poliovirus struck suddenly, without any warning. So did the “Spanish Flu.” Rather, paralytic poliomyelitis mainly struck children, adolescents and young adults. In contrast, influenza mainly threatens the elderly. And, in truth, most parents are far more emotionally invested in their children’s well-being than in that of their parents or themselves. Furthermore, the sight of a child in an iron lung or leg braces (affected legs became atrophied and deformed) was truly heart rending.

The fear evoked by poliomyelitis was permanently ended in the United States and in much of the developed world as well, by the emergence of Salk’s killed polio vaccine in 1955. Sabin’s live attenuated vaccine followed soon after. [Live vaccines generally contain attenuated (weakened) variants of the virulent virus, which can replicate and induce immunity, but which cannot cause disease.] The response of the public to Salk’s vaccine was so great that he was hailed as a “miracle worker.” Nevertheless, and despite the fact that the vaccines created by Salk and Sabin have nearly ridden the world of poliovirus, neither man would ever be recognized by the Nobel committee.

salk Salk’s public acclaim was resented by his colleagues.

Most virologists of the day strongly favored live vaccines over killed ones, based on the belief that only a live vaccine could induce a level of immunity sufficient to protect against a challenge with live virulent virus. Indeed, the effectiveness of live vaccines had been established much earlier by Jenner’s smallpox vaccine (1798) and Pasteur’s rabies vaccine (1885). Jenner’s smallpox vaccine actually contained live cowpox virus, which was similar enough immunologically to variola to protect against smallpox, while not being able to cause smallpox itself. Pasteur’s rabies vaccine contained live rabies virus that was attenuated by passages through rabbit spinal cords. [Adapting the virus to grow in rabbits attenuated its virulence in humans, while not impairing its ability to induce immunity.] So, bearing in mind the well-established precedence of attenuated vaccines, why did Salk seek to develop a killed vaccine?

In 1941, Thomas Francis, one of the great pioneers of medical virology, working at the University of Michigan, developed a killed influenza vaccine. Providentially, in the same year, Jonas Salk (recently graduated from NYU medical school) came to Francis’ laboratory for postgraduate studies. In Francis’ lab, Salk learned his mentor’s methods for producing his killed influenza vaccine and assisted in its field trials.

Salk’s experience in Francis’ laboratory led him to believe in the potential of a killed poliovirus vaccine. And, Salk learned practical procedures from Francis that would be valuable in his pursuit of that objective. These included the use of formaldehyde to kill the virus, the use of adjuvants to enhance the immunogenicity of the killed vaccine, and protocols for conducting field tests.

In contrast to Salk, Sabin firmly believed that a live attenuated vaccine would be vastly superior to a killed one. And, although Salk won the race to produce an actual vaccine, Sabin had been doing polio research well before the younger Salk emerged on the scene. Indeed, Sabin made several important contributions to the field; some of which are discussed below. For now, we mention that in 1936, Sabin and colleague Peter Olitsky demonstrated that poliovirus could be grown in cultured human embryonic nervous tissue. While this might appear to be a key step towards the development of a vaccine, Sabin and Olitsky feared that nervous tissue might cause encephalitis (inflammation of the brain and spinal cord) when injected into humans.

sabinAlbert Sabin, who developed the live polio vaccine.

John Enders, at the Children’s Hospital of Boston, is the next key player in our story. Enders believed that poliovirus should be able to grow in non-nervous tissue, particularly tissue from the alimentary canal, as suggested to him by the amount of the virus that was present in the feces of many patients. So, in 1948, Enders, and colleagues Thomas Weller and Frederick Robbins, succeeded in growing poliovirus in cultured non-nervous tissue, including skin, muscle, and kidney. As a result of Ender’s work, sufficient amounts of poliovirus could now be grown, free from the hazards of nervous tissue, thereby enabling the mass production of a vaccine.

[Aside: Enders, Weller, and Robbins maintained their tissue samples in culture using the roller culture procedure, in which a horizontally positioned bottle is laid on its side and continuously rotated around its cylindrical axis. In comparison to the older process of growing tissues in suspension, the roller culture method enabled the prolonged maintenance of the tissues in an active state and, consequently, the growth of large amounts of virus. For readers who read Renato Dulbecco and the Beginnings of Quantitative Animal Virology (on the blog), note that Dulbecco developed procedures for growing pure cell types as flat adherent monolayer cultures, thereby making possible quantitative plaque assays of animal viruses.]

In 1954, Enders, Weller, and Robbins shared the Nobel Prize in Physiology or Medicine for their contribution described above. What’s more, the Nobel award to Enders, Weller, and Robbins was the only Nobel award ever given in recognition of polio research! Ironically, Ender’s true interests actually lay elsewhere; with measles. He would later develop a measles vaccine. [Enders has been referred to as the “Father of modern vaccinology.”]

The next key player of note in our story is not a person but, rather, a foundation; the “National Foundation for Infantile Paralysis,” which led and financed the crusade against polio in the pre-NIH days of the 1950s. The National Foundation was actually an outgrowth of the Georgia Warm Springs Foundation, a charitable organization founded by Franklin D. Roosevelt, himself crippled by polio. However, after Roosevelt became president of the United States, he was too polarizing a figure (particularly after his “court-packing” scheme in 1937) to head up a philanthropic organization. Consequently, in 1938, Roosevelt announced the formation of the nonpartisan National Foundation for Infantile Paralysis.

roosevelt Photos of Franklin Roosevelt in a wheel chair are rare and were not shown to the public, which was generally unaware that he was paralyzed from the waist down.

[Aside: The National Foundation was initially funded by the contributions of wealthy celebrities who attended Roosevelt’s yearly birthday bashes. At one of these fundraisers, the vaudevillian, Eddie Cantor, jokingly urged the pubic to send dimes directly to the president. And, bearing in mind the fear evoked by polio, the public, perhaps not recognizing the joke, did exactly that, flooding the White House with nearly three million dimes. And so, the slogan “March of Dimes,” for the Foundation’s grass-roots fund-raising campaign, came to be. And, it was not coincidental that a dime (the Roosevelt dime) was issued in 1946 to memorialize the late president.

In 1950, a March of Dimes chapter in Phoenix, Arizona held a “Mother’s March on Polio,” in which volunteers went door-to-door raising money for polio research. People were urged to leave their porch lights on to show that the volunteers would be welcome. The Phoenix initiative soon spread to other locals, and the Mother’s March became a nationwide annual event.]

The role of the National Foundation went beyond merely raising money for research. It also attempted to provide direction to the research, which often placed it at odds with its grantees. This was the case because Harry Weaver, the director of research at the National Foundation, was focused on bringing a vaccine to the public. In contrast, most of the Foundation’s grantees were largely motivated by their desire to understand basic virological issues, such as poliovirus transmission, replication, and dissemination. What’s more, they believed that there was still too much to be known about poliovirus and poliomyelitis before a vaccine might be a realistic possibility.

[Aside: Apropos the sentiment of some poliovirus researchers that there was too much yet to be known before a polio vaccine might be possible, Jenner’s 1798 smallpox vaccine was developed a half century before the germ theory of disease was proposed, and 100 years before the actual discovery of viruses. It was based on the empirical observation that milkmaids seemed to be “resistant” to smallpox; apparently because they had been exposed earlier to cowpox. The initial smallpox vaccine simply contained matter from fresh cowpox lesions on  the hands and arms of a milkmaid. It was then serially passed from one individual to another; a practice eventually ended because of the transmission of other diseases. And, Pasteur’s 1885 rabies vaccine too was developed before viruses were recognized as discrete microbial entities.]

Sabin’s objection to the Foundation’s priority of having a vaccine available as quickly as possible was somewhat more personal. Since a killed vaccine should be more straightforward and, therefore, quicker to develop than an attenuated one (see below), Sabin believed that Weaver’s sense of the urgent need for a vaccine would lead him to favor supporting Salk’s killed vaccine over his attenuated one. Moreover, Sabin felt that he was being shunted aside. And, Since Sabin remained firm in his belief in the superiority of a live vaccine; he also felt that Weaver’s main concern of having a vaccine available as quickly as possible, would compromise the efficacy of the vaccine that would be implemented in the end.

[Aside: Back in the Enders laboratory, Thomas Weller and Frederick Robbins wanted to enter the polio vaccine race. But, Enders viewed the project as boring and routine; a view pertinent to the question of why Salk and Sabin were never recognized by the Nobel Committee. Furthermore, Enders didn’t believe that a killed vaccine could ever provide adequate protection against polio, or that a live vaccine would be possible without years more of research.]

Sabin’s worry that a killed vaccine would be faster to develop than an attenuated one was borne out when, in1953, Salk was preparing to carry out a field-test of his killed vaccine. Yet Sabin and other poliovirus researchers remained inclined to move slowly, placing them in opposition to Harry Weaver’s sense of urgency. Moreover, Sabin and the other polio investigators were also piqued at the National Foundation for promoting Salk’s vaccine to the public and, also, for promoting Salk himself as a miracle worker. The Foundation’s reason for publicizing Salk was to stir up public enthusiasm for its fund raising campaigns. And Salk indeed was becoming the symbol of the miracles of medical research to an admiring public.

In fairness to the polio researchers who dissented with the National Foundation’s single minded emphasis on bringing a vaccine to the public, there were valid reasons for believing that the Foundation might be moving too quickly. So, consider the following excerpts from a letter that Sabin wrote to his rival, Salk: “…this is the first time they (the Foundation) have made a public statement based on work which the investigator has not yet completed or had the opportunity to present…in a scientific journal…Please don’t let them push you to do anything prematurely or to make liters of stuff for Harry Weaver’s field tests until things have been carefully sorted out, assayed, etc., so that you know what the score is before anything is done on a public scale.”

While Sabin’s advice to Salk seems eminently sensible, Sabin had never before shown any inclination to look out for Salk’s interests. So, might Sabin be sending a non-too-subtle warning to Salk that he could either play by the traditions of the scientific community, or face the consequences of playing to the interests of the Foundation? For his part, Salk was well aware of what was happening and he was indeed embarrassed by the adulation of the press; correctly sensing that it was compromising his standing with his colleagues.

[Aside: The media, in the person of the legendary broadcaster, Edward R. Murrow, provided Salk with a notable and very satisfying moment in the public spotlight. During an April, 1955 interview on the CBS television show See it Now, Murrow asked Salk: “Who owns the patent on this vaccine?” To which, Salk replied: “Well, the people, I would say. There is no patent. Could you patent the sun?”

While Salk’s answer to Murrow endeared him even more to the public, some colleagues questioned whether it might have been disingenuous. Both the University of Pittsburgh, where Salk carried out his work, and the National Foundation, which financed it, indeed had been looking into the possibility of patenting Salk’s vaccine. But, when patent attorneys sought to determine if there was a basis for a patent, Salk readily acknowledged that his vaccine was, for the most part, based on tried and true procedures developed by others.

In point of fact, Salk’s critics held him in low esteem largely because there was little about his vaccine that was innovative. Indeed, Sabin once quipped: “You could go into the kitchen and do what he (Salk) did.” But in fairness to Salk, he never claimed that his vaccine was unique. Instead, in the face of much skepticism, his point had always been that a killed vaccine could protect against polio. He persevered and he was right.

Note that Sabin too gave his vaccine to the world gratis.]

By 1954, field tests of Salk’s vaccine went ahead on a massive scale, involving nearly 1.5 million schoolchildren nationwide. The tests were overseen by Thomas Rivers, an eminent virologist who, at the time, was Director of the Rockefeller Institute. Like most virologists, Rivers favored a live vaccine as the ultimate solution to polio. Nevertheless, he believed that the world couldn’t wait ten or more years for an ideal vaccine, when a satisfactory one might be available at present.

With 57,879 cases of poliomyelitis in the United States in 1952, the peak year of the epidemic, Harry Weaver’s sense of the urgent need for a vaccine was widely shared by the public. Unsurprisingly then, the public eagerly supported the 1954 field test of Salk’s vaccine, as indicated by the fact that 95% of the children in the test received all three required vaccinations. [Killed vaccines require multiple doses. That is so because the first dose only primes the immune system. The second or third dose then induces the primed immune system to produce protective antibodies against the virus. Inoculation with a live vaccine resembles a natural infection and, consequently, a single dose is sufficient to induce immunity.]

The field test of Salk’s vaccine was unprecedented in its size. What’s more, it was supported entirely by the National Foundation, which strenuously opposed outside interference from the federal government. In actuality, the Foundation considered federal funding for polio research to be a “Communistic, un-American…scheme.”

[Aside: President Dwight Eisenhower, a Republican and a fiscal conservative, also believed that the federal government had no proper a role in health care. Consequently, Eisenhower took little interest in his Department of Health, Education, and Welfare (HEW). What’s more, Eisenhower’s Secretary of HEW, Oveta Culp Hobby, was even more conservative in that regard than Eisenhower himself. In 1955, after the field trials showed the Salk vaccine to be a success, and with the public clamoring for it, there were insufficient amounts of the vaccine available to meet the public’s demands. Thus, even some Republicans were stunned to learn that the Eisenhower administration had taken no actions whatsoever to watch over production of the vaccine or its distribution, believing that this was in the province of the drug companies. When pressed on this, Mrs. Hobby responded: “I think no one could have foreseen the public demand.”

Not surprisingly, American drug companies lobbied intensely to keep vaccine production under their own control. A different scenario played out in Canada, where the government viewed polio as a national crisis, and took control of its vaccination program, with overwhelming public support.]

All did not go well for Salk and his vaccine after the successful 1954 field tests. In April 1955, more than 200,000 children were inoculated with a stock of improperly inactivated vaccine made by Cutter Laboratories; one of the five companies that produced the vaccine in 1955. [The others were Eli Lilly, Parke-Davis, Wyeth, and Pitman-Moore.] The Cutter vaccine caused 40,000 cases of abortive poliomyelitis (a form of the disease that does not involve the central nervous system), and 56 cases of paralytic poliomyelitis; 5 of which were fatal. What’s more, some of the children inoculated with the Cutter vaccine transmitted the vaccine virus to others, resulting in 113 more cases of paralytic poliomyelitis and 5 fatalities.

A congressional investigation blamed the “Cutter incident” on the NIH Laboratory of Biologics Control, for insufficiently scrutinizing the vaccine producers. In point of fact, the NIH did little testing on its own. Instead, it mainly relied on reports from the National Foundation, whose agenda was to proceed with the vaccinations. Yet the NIH did have an early, in-house warning of potential problems with the Cutter vaccine, which it failed to act on. Bernice Eddy, a staff microbiologist at the NIH, reported to her superiors that the Cutter vaccine caused paralysis when inoculated into monkeys. However, no action was taken in response to Eddy’s warning. [In 1959, Eddy discovered simian virus 40 (SV40) in monkey kidney tissue that was used for vaccine production. By that time, live SV40 had unknowingly been injected into hundreds of millions of people worldwide; perhaps the subject of a future blog posting.]

Salk was exonerated of any fault in the Cutter incident. Moreover, after that episode, not a single case of polio in the United States would be attributed to Salk’s vaccine. Nevertheless, while Salk’s killed vaccine was perfectly safe when properly prepared, the Cutter incident led to the perception that it was unsafe. Consequently, Salk’s killed vaccine was eventually replaced by Sabin’s live attenuated one. Ironically, as we will see, the perception that Salk’s vaccine was dangerous led to its replacement by a more dangerous one.

Sabin’s work on his live polio vaccine began in 1951 and, like Salk; he was supported by the National Foundation. Sabin’s task was more difficult than Salk’s because it is more straightforward to kill poliovirus, than it is to attenuate it. [The attenuated virus must be able to replicate in the digestive tract and induce immunity, yet be unable to damage the nervous system.] But Sabin persisted, sustained by his conviction that a live vaccine would invoke stronger, longer-lasting immunity than a killed vaccine. Sabin attenuated his vaccine by successive passages through monkey tissue, until the live virus could no longer cause paralysis when inoculated directly into chimpanzee spinal cords.

[Aside: At this early date, live-vaccine-proponents could not have known that only a live vaccine could activate T-cell mediated immunity, which is generally necessary to clear a virus infection. Instead, their preference for live vaccines was based on the simpler, but correct notion that inoculation with a live vaccine would more closely approximate a natural infection. Also, since the vaccine virus is alive, vaccinated individuals might transmit it to unvaccinated ones, thereby inducing immunity in the latter as well. On the other hand, the attenuated vaccine poses a deadly threat to individuals with impaired immune systems, such as AIDS patients and individuals on immunosuppressive regimens following organ transplants.]

In 1954, a successful small-scale test of Sabin’s vaccine was carried out, which involved thirty adult human prisoners at a federal detention facility. The promising outcome of this test warranted a larger field-trial of Sabin’s vaccine. But, several obstacles stood in the way. First, the National Foundation was not inclined to support another massive field trial, now that Salk’s vaccine was already in use. Second, the Foundation was still reeling from the Cutter incident, and had no inclination to be caught up in another such debacle. Third, it would be virtually impossible to conduct the trials in the United States, since millions of American children had already been inoculated with Salk’s vaccine. The ensuing course of events was rather remarkable.

By 1956, poliomyelitis had become a serious public health crisis in the former Soviet Union. Consequently, a delegation of Russian scientists came to the United States to meet with Salk and consult with him on how to produce his vaccine. However, the Russians were disposed to meet with other polio researchers as well. Thus, Sabin seized this opportunity to invite the Russians to visit his laboratory at the University of Cincinnati, where he was able to tout his live vaccine to them. Sabin’s pitch was apparently effective, as he secured an invitation from the Russians to visit the Soviet Union, where he spent a month, further hyping his vaccine.

[Aside: While Sabin was in Russia, the Russians requested from him a sample of his live vaccine. So, when Sabin returned to the United States, he sought permission from the State Department to send the Russians the samples they requested. The State Department approved the request; but it did so over objections from the Defense Department, which was concerned that the vaccine virus might have “biological warfare applicability.”]

With the incidence of poliomyelitis on the rise in the Soviet Union, the Soviet Health Ministry needed to quickly decide which vaccine to adopt; Salk’s or Sabin’s. The Russians were already producing the Salk vaccine, but were unable to consistently maintain its efficacy from one batch to another. So, the Soviets invited Salk to visit Russia, so that he might help them to solve the problems they were having producing his vaccine.

Salk then made a decision that he would long regret. Because of pressure from his wife to spend more time with his family, Salk turned down the Russian invitation. The upshot was that the Russians turned instead to Sabin. In 1959 they vaccinated 10 million children with vaccine strains sent to them by Sabin. Soviet results with the Sabin vaccine were so promising that the Soviet Health Ministry decided to then use it to vaccinate everyone under 20 years of age. A total of seventy-seven million Soviet citizens were vaccinated with Sabin’s vaccine, vastly exceeding the number vaccinated during field trials of the Salk vaccine in the United States.

The U.S. Public Health Service did not endorse the Sabin vaccine for use in the United States until 1961. By then, the Salk vaccine had virtually eliminated polio from the country. Nevertheless, Sabin’s vaccine supplanted Salk’s in the United States and in much of the rest of the world as well.

Yet all did not go well with Sabin’s vaccine either. As noted above, after the Cutter incident, there were no cases of poliomyelitis in the United States that could be attributed to Salk’s vaccine. In contrast, Sabin’s vaccine caused about a dozen polio cases per year, a frequency of about one case per million vaccinated individuals. At least some of these cases resulted from the ability of the attenuated virus to revert to a more virulent form. What’s more, reverting viruses posed a threat to non-vaccinated individuals in the population. For instance, in 2000/2001, there were 21 confirmed cases of poliomyelitis in the Dominican Republic and Haiti, which were traced to a single dose of the Sabin vaccine that was administered during the preceding year. [As noted in an above Aside, since the Sabin vaccine is alive, vaccinated individuals might transmit the vaccine virus to unvaccinated individuals.]

In actual fact, the few cases of poliomyelitis that now occur in the West are vaccine-related, resulting from the rare reversions of Sabin’s vaccine. Ironically, the Sabin vaccine, which played a crucial role in the near eradication of polio from the world, had become an obstacle to the complete eradication of the virus. In 2000, the U.S. Centers for Disease Control (CDC) recommended the complete return to the Salk vaccine in the United States. However, the Sabin vaccine would continue to be used in much of the developing world.

[Aside: Several polio hotspots remain in the world. Three major ones are Pakistan, Afghanistan, and Nigeria. Recent outbreaks have also occurred in Syria and Somalia. In each of these instances, social and political climates make it difficult to carry out eradication campaigns.

As recently as March 2014, militants attacked a polio vaccination team in northwest Pakistan, detonating a roadside bomb and then opening fire on their convoy, killing 12 of their security team, and wounding dozens more. Some Pakistani religious leaders denounced the vaccination campaign in Pakistan as a cover for spying or as a plot to sterilize Muslim children.

In the developed world there is a very different problem. Ironically, the great success with which the polio vaccines eradicated the virus in the West has created conditions there in which poliomyelitis might make a most unwelcome return. That has come about because too many parents in the developed world now view polio as ancient history, and have become complacent about having their children vaccinated. What’s more, some parents are heeding unsubstantiated warnings that the risks of vaccines are greater than the risks of the viruses. Consequently, the frequency of vaccinated individuals in the West is declining to the point where the West may be susceptible to outbreaks sparked by imported cases. These issues will be discussed at length in a subsequent posting.]

We turn now to an issue raised at the outset of this posting; neither Salk nor Sabin was recognized by the Nobel Committee for his contribution. That is so, despite the fact that their individual efforts, taken together, have virtually eliminated polio from the world.

Max Theiler, at the Rockefeller Institute, is relevant regarding the Nobel issue, and for several other reasons as well. First, Theiler took an early interest in Sabin’s career during Sabin’s years at the Rockefeller (1935 to 1939). Second, during those years Theiler was working on a live attenuated vaccine for yellow fever. Like most virologists of the day, Theiler believed that only a live vaccine could provoke significant long-lasting immunity. And, Theiler’s thinking on this matter likely influenced Sabin’s later approach to a polio vaccine. Thirdly, and important in the current context, in 1951 Theiler was awarded the Nobel Prize in Physiology or Medicine for his yellow fever vaccine. Fourth, Theiler’s Nobel Prize was the only one ever awarded for the development of a virus vaccine!

Why was Theiler’s Nobel award the only one ever given for the development of a virus vaccine? In addition, recall that John Enders, Thomas Weller, and Frederick Robbins shared the 1954 Nobel Prize for Physiology or Medicine, for demonstrating that poliovirus could be propagated in non-nervous tissue. Moreover, the Nobel Prize shared by Enders, Weller, and Robbins was the only one ever given in recognition of polio research! Why weren’t Salk and Sabin recognized as well? Didn’t they also contribute substantially “to the benefit of mankind;” a standard for the award, as specified by Alfred Nobel?

Apropos these questions, it may be relevant that Alfred Nobel also specified that the prize for physiology or medicine should recognize a “discovery” per se. With that criterion in mind, the Nobel committee may have viewed the contributions of Salk and Sabin as derivative, requiring no additional discovery. In contrast, the discovery of Enders, Weller, and Robbins, refuted the previously held belief that poliovirus could be grown only in nervous tissue; a breakthrough that paved the way to the vaccines.

But then, what was there about Theiler’s yellow fever vaccine that might be considered a discovery? Hadn’t Pasteur developed an attenuated Rabies vaccine in 1885? And, what of Jenner’s earlier 1798 smallpox vaccine, comprised of live cowpox virus?

To the above points, Sven Gard, at the Karolinska Institute, and a member of the Nobel committee for Physiology or Medicine, wrote the following in his evaluation of Theiler’s prior 1948 Nobel nomination: “Theiler can not be said to have been pioneering. He has not enriched the field of virus research with any new and epoch-making methods or presented principally new solutions to the problems, but he has shown an exceptional capacity to grasp the essentials of the observations, his own and others, and with safe intuition follow the path that led to the goal.”

Despite the seeming inconsistency between Gard’s comments and Nobel’s instruction that the prize be awarded for a discovery, Gard nonetheless concluded that Theiler’s contributions indeed merited the Nobel award. [Incidentally, Theiler’s 1948 Nobel nomination was a detailed six-page-long document, written and submitted on his behalf by Albert Sabin!]

To the same point, Hilding Bergstrand, also at the Karolinska Institutet, and chairman of the Nobel Committee for Physiology and Medicine, said the following during his otherwise laudatory speech honoring Theiler at the 1951 Nobel Prize ceremony: “The significance of Max Theiler’s discovery must be considered to be very great from the practical point of view, as effective protection against yellow fever is one condition for the development of the tropical regions—an important problem in an overpopulated world. Dr. Theiler’s discovery does not imply anything fundamentally new, for the idea of inoculation against a disease by the use of a variant of the etiological agent which, though harmless, produces immunity, is more than 150 years old.”

Even Theiler himself agreed that he had not done anything fundamentally new. But then, what might Bergstrand have had in mind when referring to Theiler’s discovery? Perhaps it was Theiler’s finding that passage of the Asibi strain of yellow fever virus in chick embryos, which were devoid of nervous systems, generated viable, non-neurotropic attenuated yellow fever virus. If so, then did that discovery fulfill the condition for the Nobel award, as specified by Alfred Nobel? And, if that is the case, then might this discovery have been what makes Theiler’s contribution more worthy than those of Salk and Sabin in the eyes of the Nobel committee? [A more detailed account of Max Theiler’s yellow fever vaccine, particularly with regard to the “discovery” noted here, can be found in The Struggle Against Yellow Fever: Featuring Walter Reed and Max Theiller, now on the blog.]

The seemingly trivial distinction between the worthiness of Theiler’s contribution from that of Salk and Sabin, suggests that we may need to look elsewhere for answers to why Salk and Sabin were bypassed by the Nobel committee. One reason suggested in the case of Salk is that in the elitist world of big-time science, he had never spent time at a prestigious Research institution like the Rockefeller. Yet he did carry out postgraduate studies in association with the eminent Thomas Francis. So perhaps he was passed over by the Nobel committee because it did not see anything innovative about his vaccine. Or, perhaps it was because he allowed himself to be promoted as a celebrity by the March of Dimes, thereby causing resentment among his colleagues.

But, how then might we explain the case of Sabin? Sabin had not been used by the National Foundation to promote its fund-raising. And, he had done research at the Rockefeller Institute. Moreover, Sabin made seminal contributions to the poliovirus field before and after beginning his vaccine work. As noted above, Sabin and Peter Olitsky demonstrated that poliovirus could be grown in cultured human embryonic nervous tissue. Moreover, Sabin provided experimental evidence that the poliovirus port of entry is the digestive tract, rather than the respiratory tract, as was previously thought. And, Sabin established that the incidence of poliomyelitis tended to be highest in urban populations which had the highest standards of sanitation.

[Aside: Sabin’s finding, that the poliovirus route of entry is via the alimentary tract, validated the premise that poliomyelitis might be prevented by a live oral vaccine. In contrast, Salk’s killed vaccine needed to be injected. An advantage of a vaccine being administered by the oral route, particularly in developing countries, is that trained medical personnel are not required for its administration. On the other hand, the killed vaccine is safer. The few cases of poliomyelitis that now occur in the West are vaccine-related, resulting from rare reversions to virulence of the attenuated virus.]

[Aside: Why was the incidence of poliomyelitis highest in urban populations that had the highest standards of hygiene? Polio infection tends to be milder in the very young, perhaps because they are partially protected by maternal antibodies. But, in areas with high standards of hygiene, infection tends to occur later in life, when maternal antibodies have waned, and the infection can then be more severe.

Before this was appreciated, poliomyelitis was thought to originate in the slums and tenements of cities, and then spread to the cleaner middle-class neighborhoods. Thus, during polio outbreaks in New York City, there were instances when slums and tenements were quarantined, and city dwellers fled to the suburbs, all to no avail.]

Were Sabin’s discoveries noted above, taken together with his vaccine, worthy of a Nobel Prize? In any case, Sabin indeed had been nominated for the Nobel award by numerous colleagues, including Enders. So, why was Sabin never awarded the Nobel Prize? Perhaps the Nobel committee could not recognize Sabin without also recognizing Salk, which it may have been reluctant to do for reasons noted above. Or, as has been suggested, the continual back-and-forth carping between supporters of Salk and Sabin may ultimately have diminished enthusiasm in Stockholm for both of them.

Salk (in 1956) and Sabin (in 1965) each received the prestigious Lasker Award for Clinical Research (often seen as a prelude to the Nobel) and, earlier, in 1951, Sabin was elected to the U.S. National Academy of Sciences. In contrast, Salk was the only prominent polio researcher not elected to the Academy. And regarding the Nobel Prize, Salk once joked that he didn’t need it, since most people thought he had already won it.

In 1963 Salk founded the prestigious Salk Institute for Biological Studies in La Jolla, California. Francis Crick (1), Renato Dulbecco (2), and Leo Szilard (3), each of whom is featured elsewhere on the blog, were among the eminent scientists recruited by Salk to the La Jolla campus. Bearing in mind Salk’s alienation from other medical researchers of the day, we might enjoy his remark “I couldn’t possibly have become a member of this institute if I hadn’t founded it myself.” Jonas Salk died of congestive heart failure in 1995 at the age of 80. He remains one of the most venerated medical scientists ever.

salk instSalk Institute for Biological Studies

[Aside: Salk married Dora Lindsay in 1939, right after he graduated from NYU medical school. But, the marriage eventually fell apart, and the couple divorced in 1968.

In 1970, Salk married the artist Francois Gilot, who had been the mistress of Pablo Picasso for nearly ten years and with whom she had two children. Salk and Gilot met in 1969, at the home of a mutual friend in Los Angeles. They remained married until Salk’s death in 1995.

The following is from an April 27, 2012 article in Vogue by Dodie Kazanjian, entitled Life after Picasso: Francois Gilot.

“On a trip to Los Angeles in 1969, a friend introduced her to Jonas Salk. She had no interest in meeting him—she thought scientists were boring. But soon afterward, he came to New York and invited her to have tea at Rumplemayer’s. ‘He didn’t have tea; he ordered pistachio and tangerine ice cream,’ she recalls. ‘I thought, Well, a scientist who orders pistachio and tangerine ice cream at five o’clock in the afternoon is not like everybody else!’ He pursued her to Paris and a few months later asked her to marry him. She balked. “I said, ‘I just don’t need to be married,’ and he said, ‘In my position, I cannot not be married.’ He gave me two pieces of paper and told me to write down the reasons why I didn’t want to get married.” She complied. Her list included: ‘I can’t live more than six months with one person’; ‘I have my own children’; ‘I have my career as a painter and have to go here and there’; ‘I’m not always in the mood to talk. Et cetera, et cetera, et cetera.’

Salk looked at the list and said he found it ‘quite congenial.’ They were married in 1970 and were together until he died in 1995. ‘It worked very well,’ she says, because after all we got along very well.’”]

Albert Sabin became president of the prestigious Weizmann Institute of Science in Israel, but stepped down in November 1972 for health reasons. He passed away in 1993 at the age of 86. Unlike in the case of Salk, and despite the fact that he never was awarded the Nobel Prize, Sabin’s standing among his colleagues always remained high.

Before concluding, we note two other important contenders in the quest for a polio vaccine. The first of these was Isabel Morgan, the daughter of the great geneticist, Thomas Hunt Morgan. Isabel Morgan nearly produced a killed polio vaccine before Salk succeeded in doing so. Working at Johns Hopkins, she generated formalin-inactivated poliovirus preparations that indeed protected monkeys against intracerebral injections of live poliovirus. However, Morgan gave up her research in 1949 to marry and raise a family. At that time, Salk had barely begun his work. But, if Morgan had remained in the race, Salk may yet have beaten her to the finish line, since she was reluctant to test her vaccine on human subjects.

Hilary Koprowski was the other noteworthy contender in the race to a polio vaccine. Koprowski was a Polish Jew who immigrated to Brazil in 1939, after Germany invaded Poland. He later came to the United States, where, in 1945, he was hired by Lederle Laboratories to work on a project to develop a live polio vaccine. Koprowski’s foray into polio had a few interesting happenings. Moreover, he went on to have a renowned career as a virologist. Thus, we discuss him in a bit more detail.

[Aside: Salk and Sabin also were Jewish. And Sabin too was born in Poland. In 1921 he immigrated with his family to the United States, at least partly to escape persecution of Jews in his birth-land.]

Koprowski began his work at Lederle before John Enders developed methods for growing poliovirus in monkey kidney cell cultures. Consequently, Koprowski attenuated his live vaccine by passaging it in mouse brains in vivo. In 1950, several years before Sabin’s vaccine was ready for testing, Koprowski found that his vaccine indeed protected chimpanzees from challenge with virulent poliovirus. Koprowski then tested his live vaccine in humans; first on himself, and then on 19 children at a New York State home for “feeble minded” children.

Koprowski was still an unknown figure in the scientific community when he made the first public presentation his test findings. This happened at a 1951 National Foundation roundtable that was attended by the major polio researchers of the day, including Salk and Sabin. The conferees were aghast upon hearing that Koprowski had actually tested his live vaccine, grown in animal nerve tissue, on children. Koprowski’s response was simply that someone had to take that step. Also, it didn’t help Koprowski’s standing with his academic colleagues that he was employed by Lederle. In those pre-biotech days, he was looked down on as a “commercial scientist.”

Human testing was of course a necessary step in the development of this or any human vaccine. What’s more, using cognitively disabled children as test subjects was a common practice back then. So, the actual concern of Koprowski’s colleagues was that he inoculated human subjects with a vaccine that was grown in animal brains. Koprowski also may have been treading on shaky legal ground, since it is not clear whether he ever obtained consent from the children’s parents.

[Aside: The only guidelines for such tests back then were the so-called Nuremburg Code of 1947, which was formulated in response to Nazi “medical” experiments. Informed consent was one of the Nuremburg guidelines, which, in the case of children, meant consent from a parent or guardian. Note that federal approval was not required to test vaccines or drugs in those days.]

Irrespective of whatever uproar Koprowski caused by testing his vaccine on helpless institutionalized children, he indeed had a live polio vaccine in 1949; several years before Salk and Sabin brought out their vaccines. However, Koprowski’s vaccine began its demise soon afterwards. A small field trial in Belfast showed that the attenuated virus could revert to a virulent form after inoculation into humans. But, bearing in mind that there was not yet any alternative to his vaccine, Koprowski firmly believed that the greater risks of natural poliovirus infections justified its use.

The fate of Koprowski’s vaccine was sealed in 1960, when the U.S. Surgeon General approved the Sabin vaccine for trial manufacture in the United States, while rejecting Koprowski’s vaccine on safety grounds. Tests showed that Sabin’s vaccine was the less neurovirulent of the two vaccines in monkeys. Sabin had carefully tested plaque-isolated clones of his attenuated viral populations for neurovirulence in monkeys, and he then assembled his vaccine from the least neurovirulent of these clones. Moreover, by this time millions of children in the Soviet Union had had been successfully immunized with the Sabin vaccine.

Koprowski left Lederle Laboratories in 1957 after clashing with its management. After that, he became Director of the Wister Institute in Philadelphia. He then transformed the then moribund Wistar into a first class research organization.

The relationship between Koprowski and Sabin was quite adversarial at the time their vaccines were in competition, but they later became friends. In 1976, Koprowski was elected to the U.S. National Academy of Sciences, an honor shared with Sabin, bit never afforded to Salk.

Here is one last bit on Koprowski. Recall that early lots of the Salk and the Sabin vaccines unknowingly contained live SV40, which had been injected into hundreds millions of people worldwide. While the unknown presence of a live tumor virus in a vaccine must be one of a vaccinologist’s worst nightmares, this finding did not attract the attention of the public. In contrast, a 1992 article in Rolling Stone, which attributed the emergence of HIV to Koprowski’s polio vaccine, created a sensation. The premise of the article was that Koprowski’s vaccine was produced in chimpanzee cells that were contaminated with simian immunodeficiency virus (SIV), which then mutated into HIV when inoculated into humans. As might be expected, there was no evidence to support that premise. Indeed, PCR analysis could not detect SIV or HIV in the supposedly contaminated vaccine lots, and records from Koprowski’s laboratory showed that his vaccine was never grown in chimpanzee cells. So, faced with the possibility of a lawsuit, Rolling Stone issued a retraction.

Readers, who enjoyed the above account of the rivalry between Jonas Salk and Albert Sabin, may also enjoy the account of the rivalry between Robert Gallo and Luc Montagnier in Who Discovered HIV? More on the same topic can be found in How the Human Immunodeficiency Virus (HIV) Got its Name. For a very different kind of rivalry, that between Howard Temin and David Baltimore, see Howard Temin: In From the Cold.

1. Howard Temin: “In from the Cold” On the blog.

2. Renato Dulbecco and the Beginnings of Quantitative Animal Virology On the blog.

3. Max Delbruck, Lisa Meitner, Niels Bohr, and the Nazis On the blog.