Jonas Salk

Eyridiki Sellou | Oct 12, 2022

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Jonas Edward Salk (New York, Oct. 28, 1914 - La Jolla, June 23, 1995) was an American virologist, bacteriologist, and researcher who invented the first polio vaccine.

Until 1955, when its vaccine was introduced, polio was considered the most frightening public health problem in the postwar United States of America. The annual epidemics were increasingly devastating: the one in 1952 was the worst in the nation's history. Of the nearly 58,000 cases reported that year, 3,145 people died and 21,269 were left with mild or disabling paralysis. Most of the victims were children. Scientists scrambled to find a way to prevent or cure the disease. U.S. President Franklin Delano Roosevelt was perhaps the world's best-known victim and founded the organization that would fund vaccine development.

In 1947 Salk accepted a position at the University of Pittsburgh School of Medicine and the following year undertook a project funded by the National Foundation for Infantile Paralysis to determine the number of different types of the polio virus. Salk also saw in that goal an opportunity to devote himself to the development of a polio vaccine and, together with the qualified research team he chose to work alongside him, devoted himself to the project for the next seven years. The test bed set up to test Salk's vaccine was, as historian William O'Neill reported, "the most elaborate program of its kind in history, involving 20,000 physicians and public health officials, 64,000 school employees, and 220,000 volunteers." More than 1,800,000 school children took part in the experiment. When news of the vaccine's success was made public on April 12, 1955, Salk was hailed as "the miracle man," and the day "became almost a national holiday." His only goal had been to develop a safe and effective vaccine as quickly as possible, with no interest in personal profit. When asked in a television interview who owned the vaccine patent, he replied, "People, I guess. There is no patent. Can you patent the sun?"

In 1960 he founded the Salk Institute for Biological Studies in La Jolla, California, which is still a center for medical and scientific research. He also continued to conduct research and publish books, Man Unfolding (1972), The Survival of the Wisest (1973), World Population and Human Values: A New Reality (1981), and Anatomy of Reality: Merging of Intuition and Reason (1983). Salk spent the last years of his life researching an HIV vaccine.

Jonas Salk was born in New York City on October 28, 1914, to Daniel and Dora Salk. His parents came from Lithuanian immigrant families and were Ashkenazi Jews. In fact, according to historian David Oshinsky, Salk grew up in New York City's "immigrant Jewish culture." He had two younger brothers, Herman and Lee. The family moved from East Harlem to the Bronx, spending only a short time in Queens.

High School

At the age of thirteen, Salk was admitted to Townsend Harris High School, a public school for particularly intellectually gifted students. Named after the founder of the City College of New York (CCNY), the school was, Oshinsky writes, "a springboard for talented sons of immigrants who lacked the money-and the noble birthright-to attend a private school of excellence." According to one of his fellow students, Salk "was known as a perfectionist who read anything that came his way." Students were forced to compress a four-year curriculum into only three years. As a result, most dropped out or were expelled for poor performance, in spite of the school's motto: "Study, study, study." Of those who graduated, however, most earned grades sufficient to enroll at CCNY, known to be a highly competitive college.


Salk enrolled at the City College of New York and earned an academic degree in science in 1934. Oshinsky writes that "for working-class immigrant families, City College represented the pinnacle of public higher education. Getting in was difficult, but tuition was free. Competition was tough, but the rules were applied fairly. No one was recommended by birth." At his mother's urging, he put aside his aspiration to become a lawyer and focused on the courses required for admission to medical school. However, according to Oshinsky, the resources available at City College were "barely second-rate." There were no research labs, the library was inadequate. "What made that place special was the student body that had fought so hard to get in. From their ranks, between the 1930s and 1940s, emerged a wealth of intellectual talent, including more Nobel Prize winners-as many as eight-and more Ph.D. recipients than any other public college except the University of California at Berkeley." Salk entered it at the age of fifteen, "a common age for a freshman who had skipped several grades along the way." As a child, he had shown no interest in medicine or science in general. He said in an interview with the Academy of Achievement, "I was simply interested in human things, the human side of nature, if you will, and I continue to be interested in that."

Medical School

According to Oshinsky, New York University based its modest reputation on celebrated alumni, such as Walter Reed, who collaborated in the victory over yellow fever. The tuition fee was "relatively low and, better yet, did not discriminate against Jews, whereas most of the surrounding medical schools - Cornell, Columbia, University of Pennsylvania, Yale - imposed strict quotas on them." Yale, for example, in 1935 accepted 76 applicants out of a total of 501. Although 200 of them were Jewish, only five were admitted. During his years at New York University School of Medicine Salk became absorbed in research, even taking a year off to study biochemistry. Later he focused more on studying bacteriology, which had replaced medicine as his primary interest. He said his desire was to help humanity in general rather than individual patients. As Oshinsky writes, "it was laboratory work, in particular, that gave a new direction to his life."

Postgraduate research

During his last year in medical school, he chose a bimonthly elective in the laboratory of Dr. Thomas Francis. Francis had recently joined the faculty after working for the Rockefeller Foundation, where he had discovered the influenza B virus. According to Bookchin, "The two-month job in Francis' lab was Salk's first introduction to the world of virology, and he was irresistibly drawn to it." After graduation he began working at Mount Sinai Hospital in New York, once again in Francis' lab. Few hospitals in Manhattan enjoyed Mount Sinai's reputation, particularly among the city's Jews. Oshinsky interviewed a friend of Salk's who said, "Doing an internship there was like playing for the New York Yankees Only leading men from the nation's medical schools dared to forward the application." Although focused primarily on research, Salk "displayed amazing skills as a clinician and surgeon." But it was "his leadership as chairman of the intern staff at Mount Sinai that best defined him in the eyes of his colleagues." The most pressing issue for many of them in 1939, for example, was not the fate of the hospital but the future of Europe after Nazi Germany invaded Poland. And so it was that "several trainees responded by wearing badges indicating their support for the Allies," but the hospital director ordered them to remove them so as not to upset the patients. They then exposed the problem to Salk, who urged them to wear the badges as a gesture of solidarity. The hospital administrators backed down and there was no further interference from the director.

Research career

At the end of his residency, Salk began to submit applications for employment as a researcher, but found that many of the jobs he wanted were precluded because of the "Jewish quotas" prevalent in many medical research institutions. Nor could he apply at Mount Sinai, as the hospital's policy prohibited hiring trainees. As a last resort, he turned to Dr. Francis, but he had left New York the previous year after accepting an offer to head the School of Public Health at the University of Michigan.

However, he did not abandon his protégé. "He got him some money and offered him a job" on a project in Michigan funded by the military to develop a vaccine for influenza. Salk and Francis eventually perfected a vaccine that was soon widely used by military forces. The young researcher had been responsible for researching and isolating one of the flu strains that was included in the final vaccine. Beginning in 1947, Salk decided to find an institution in which he could run his own laboratory. After three rejections, he received an offer from William McEllroy, the dean of the University of Pittsburgh School of Medicine. He accepted, and in the fall of that year he left Michigan and settled in Pennsylvania. But the proposal was not quite what he expected. After arriving in Pittsburgh, "he found that he was relegated to cramped and unequipped quarters in the basement of the old Municipal Hospital," Bookchin writes. As time passed and with the financial help of a wealthy local family (the Mellons), however, he was able to build a functioning virology laboratory, where he continued his research on fever vaccines. Later, he was contacted by the director of research at the National Foundation for Infantile Paralysis, who suggested that he participate in a foundation research project on polio desired by President Franklin Delano Roosevelt, since at the time it was believed that he himself was a victim of the disease. Salk readily accepted the offer, saying he "would be happy to work on this important project."

In 1956, Wisdom magazine edited a cover story on Salk that summarized some of the reasons behind his desire to do research:

There are two kinds of specialists in medicine. There are those who fight disease day and night, who assist humanity in times of despair and anguish, and who preside over the awesome events of life and death.

Others work in the silent detachment of the laboratory; their names are often unknown to the public, but their research could have momentous consequences.

The worst evil of the postwar era

Polio baffled researchers for years. The first cases were recorded starting in 1835, and its spread was steady and increasing. It took a long time to realize that the virus was transmitted through feces and secretions from the nose and throat, settled in the intestines and then moved up to the brain and spinal cord. In the United States, during the polio epidemics of 1914 and 1919, doctors and nurses conducted house-to-house inspections to identify all infected persons. Children suspected of being sick with polio were taken to the hospital and their families were quarantined until it was certain that they were not infected, even if it meant that they could not go to the funeral if the child died in the hospital.

U.S. historian William O'Neill noted how epidemics were increasingly violent, and their victims were too often children. In the twenty states where the disease recurred in 1916, there were a total of 27,363 cases. In New York alone there were 9,023 new cases: for a large number of them the disease led victims to paralysis, and for 28 percent it had a fatal outcome. Nevertheless, polio did not gain national attention until 1921, when Franklin Delano Roosevelt, soon to become governor of New York, fell ill. At age 39, Roosevelt became severely paralyzed and spent most of his presidency in a wheelchair. Later, as more states began to report cases of the disease, the number of victims grew. By 1952 nearly 58,000 cases were reported, and polio became the disease that killed more children than any other. In some parts of the country, concern almost assumed the proportions of collective panic. "Parents did not send their children to school, and children avoided parks and swimming pools and played only in small groups and with close friends."

The beginnings

"Since panic brought no good and quarantine seemed futile, parents realized that they could best protect their children only by contributing to the discovery of a vaccine or, perhaps, a cure." The public soon realized that this kind of research required "a lot of money" and an "army of devoted volunteers." The battle against polio did not really begin until 1938, when the National Foundation for Infantile Paralysis was born, headed by Basil O'Connor, former law adviser to President Roosevelt, America's most famous polio victim. That same year, the first fundraising program ("March of Dimes") was established, with radio networks offering free 30-second promotional spots during which listeners were invited to send ten cents on the dollar. The White House received 2,680,000 letters within a few days. Fear of the disease increased year by year, and so did the funds to fight it: from $1.8 million to $67 million in 1955. Research continued during those years but, as O'Neill writes, "Everything scientists were convinced of at first was wrong, and this led them down many dead ends . What's more, most of the researchers were experimenting with highly dangerous live vaccines. In one test six children died and three were left crippled." "This was the situation when Jonas Salk, a young physician in charge of a virology laboratory at the University of Pittsburgh, decided to use an inactivated, safer vaccine," O'Neill reports. Despite a general lack of enthusiasm for this approach, O'Connor generously funded Dr. Salk.

After successful laboratory trials on animals, the vaccine was to be tested on humans. "Who would take this risk?" wondered writer Dennis Denenberg. "Dr. Salk did , along with his wife and children, who agreed to become human guinea pigs." In November 1953, at a conference at the Waldorf-Astoria Hotel in New York, he said, "I will be personally responsible for the vaccine." It was critically important that he earn the trust of the American public for the experiments and mass testing that would be required. As one of his colleagues remarked, "The man really suffered when dealing with cases of paralysis. You could see him thinking, 'My God, this could all be avoided.'" An article in Wisdom reported that "he at one point even thought of giving up the research: but as he sat in a park and watched children play, he realized how important that work was: there were thousands of adults and children who would never walk again, whose bodies would remain inert. He became aware of his terrible responsibility, and so he persevered in his efforts with renewed vigor." After preliminary results, in 1954, as polio was destroying the lives of American children more than any other disease, Salk's vaccine was ready for field trials.

First human trials

"More American citizens took part in the funding, development, and testing of the polio vaccine than had participated in the presidential election." At least one hundred million people had contributed to the March of Dimes, and seven million of them had also donated time and effort to the cause: fundraisers, volunteers at clinics and data centers, as well as all health care personnel. Historian Doris Fleischer writes that "When O'Connor realized that success seemed imminent, he allowed the foundation to go into debt to fund the final research required to develop Salk's vaccine. His passionate devotion to the cause became almost obsessive when his sister, a mother of five, confided in him that she had contracted the disease, telling him, "I caught some of your polio." Salk worked sixteen-hour days, seven days a week, for years. The test results were eventually deemed a success, and so Salk lived up to Basil O'Connor's confidence.

The announcement of the test results

On April 12, 1955, Dr. Thomas Francis, Jr. reviewer of the test results, declared that the vaccine was safe and effective. "The announcement was made at the University of Michigan, exactly ten years to the day of President Roosevelt's death. Five hundred people, including one hundred and fifty journalists, radio reporters, and television reporters, cluttered the lecture hall; sixteen cameras were positioned on a long scaffold in the back; and 54,000 doctors, seated in movie theaters across the country, watched the broadcast from closed-circuit television. The multinational pharmaceutical company Eli Lilly and Company paid $250,000 to have the event broadcast. Americans turned on their radios, department stores set up loudspeakers, and judges suspended court proceedings. Europeans were also tuned in to the Voice of America. About this, Paul Offit reports, "The presentation was obscure, but the conclusion was clear: the vaccine worked. Inside the auditorium, Americans greeted the result with tears of joy. As Thomas Francis stepped down from the podium, church bells rang across the country, factories observed a moment of silence, synagogues and churches held prayer meetings, and parents and teachers wept. One shopkeeper painted an inscription on his window, "Thank you, Dr. Salk." It was as if the war was over Dr. Francis reported that the vaccine was effective in 80-90% of cases based on results in eleven states. Overall, it was administered to more than 440,000 children in forty-four states, three Canadian provinces and Helsinki, Finland. After the announcement, when asked if the vaccine's effectiveness could be improved, Salk replied, "Theoretically, the 1955 vaccines and vaccination procedures could be brought up to 100 percent protection."

The nation celebrates

A few minutes after Francis' declaration, news of the event was already spreading through radio news and television news. According to Debbie Bookchin, "from one end of the nation to the other there were spontaneous celebrations . Any activity stopped as the news broke: the mayor of New York City interrupted a city council meeting to make the happy announcement, adding, 'I think we can all say we are extremely proud that Dr. Salk is a graduate of City College. "From the next morning," Bookchin writes further, "politicians all over the country were scrambling to find a way to congratulate Salk, and several of them were proposing to bestow special honors and medals on him. A ceremony had already been scheduled at the White House to present Salk with a special presidential medal designating him a benefactor of humanity." His success was also declared "a victory for the entire nation." Jonas Salk became "world famous overnight and was showered with honors." The governor of Pennsylvania had a special medal minted, and the state legislature awarded him a university professorship. However, the city of New York did not allow him to accept a parade in his honor on par with a celebrity. Instead, eight scholarships were established in his name for medical students. He also received a Presidential Citation and the first U.S. Congressional Medal for "Distinguished Civilian Service." O'Neill also recounts that "April 12 had almost become a national holiday: people observed a few minutes of silence, rang bells, blew trumpets and whistles, fired blanks, closed schools or called fervent assemblies within them, made toasts, hugged children, attended churches, smiled at strangers and forgave enemies."

By July, film companies were already battling to grab the rights to a film-biography. Twentieth Century-Fox began writing a screenplay while Warner Bros. claimed primacy over the title "The Triumph of Dr. Jonas Salk" already shortly after the formal announcement of the vaccine discovery. On May 6, 1985, President Ronald Reagan proclaimed that day "Jonas Salk Day."

Global acceptance and hope

Six months before Salk's announcement, optimism and confidence were so widespread that the Polio Fund in the United States had already signed a contract to purchase enough doses of Salk's vaccine to immunize nine million children and pregnant women for the next year. And around the world, the official news immediately led to an international rush for vaccination. "Israel had committed to purchasing the vaccine just days before the release of the final report, and now Canada, Sweden, Denmark, Norway, West Germany, the Netherlands, Switzerland, and Belgium were also announcing plans to begin polio immunization campaigns immediately, or at least as soon as possible, using Salk's vaccine. It was a true miracle of modern medicine." Because Salk was the first to demonstrate that injecting a killed virus could avert the danger of contracting the disease, medical historian Paul Offit wrote in 2007 that "for this observation alone, he should have won the Nobel Prize." Virologist Isabel Morgan had previously outlined this discovery in her publications, but had never tested the vaccine on humans. Despite this, her work was a key link in the chain of progress toward the inactivated polio vaccine for humans later developed and tested by Salk.

By the summer of 1957, more than two years later, one hundred million doses had been distributed in the United States, and "complications reported after their administration were remarkably rare," as outlined at the International Conference on Poliomyelitis in Geneva. Denmark "reported only a few sporadic cases among the two and a half million individuals who had received the vaccine." Australia had reported virtually no cases of polio the previous summer. Other countries where the vaccine was not yet in use, however, faced new epidemics: in 1957 in Hungary an international emergency response was needed. By the first half of the year there were 713 reported cases, with a 6.6 percent mortality rate, and the summer months when the infection would peak were still to come. Canada sent doses of vaccine in a refrigerated plane, while Britain and Sweden sent hyperbaric chambers. In 1959, during an outbreak in Canada, "masked bandits" stole 75,000 doses of Salk's vaccine from a university research center in Montréal.

Successes in the rest of the world

By the end of 1990 it was estimated that, worldwide, 500,000 cases of paralysis due to polio had been prevented each year through immunization programs implemented by the World Health Organization, UNICEF and many other organizations. By 2002, more than 500 million children had been vaccinated in 93 countries, and in December there were only 1924 cases worldwide, 1599 of them in India. However, there were still six countries where polio was suspected to be an endemic disease: Afghanistan, Egypt, Niger, Nigeria, Pakistan, and Somalia.

In 1988 several international medical organizations launched a campaign to eradicate the disease on a planetary scale, as had happened with smallpox. By 2003 polio had been defeated in all countries except Afghanistan, India, Nigeria and Pakistan.

New medical research projects

Just two weeks after the vaccine was announced, Senator Hubert H. Humphrey (Democrat, Minnesota) urged President Dwight D. Eisenhower to show the nation's gratitude to Dr. Jonas Salk for his new polio vaccine by "loosening the strings" of medical research. Salk knew it would take time to test his theories and improve the vaccine. Several questions remained to be answered: how long will the vaccine's effect last? Are there children who cannot be vaccinated? What improvements were possible? In the years that followed, while trying to perfect the polio vaccine, Salk was unofficially working on a cure for cancer. A 1958 New York Times article confirmed that he was conducting experiments on some sick patients. The news leaked after a Pittsburgh newspaper, the Sun-Telegraph, reported that Salk was giving injections to children with cancer. Salk later stated: "It is true that we are conducting experiments on many people with different types of tumors or pseudotumor diseases, but we have no treatment for cancer. Our studies are strictly exploratory in nature." In 1965, he also said that "a vaccine for the common cold is only a matter of time and solving some technical problems."

Sabin's final victory and vaccine controversy

Years before Salk's vaccine was officially declared safe, Dr. Albert Sabin had been engaged in research in that field, using a live virus, as opposed to Salk's killed virus. There was open hostility between them: Debbie Bookchin writes that after a speech Salk gave at a medical conference, "Sabin mounted a full-scale offensive, engaging in a pointed demolition of his presentation. Despite this, the National Foundation gave Salk full credit. Here at last, they said, was a polio researcher who had accomplished something." By 1962 polio had been all but defeated, with only 910 cases reported - 37,476 fewer than in 1954. "It's a matter of principle," Salk said. "This is not a dispute between Sabin and me, a competition between two people . I have worked with influenza viruses, helping to establish the efficacy of an inactivated vaccine. I showed that it could be 100 percent effective if the amount of virus killed in the vaccine was sufficient." That same year the New York State Health Department recommended that "Salk's vaccine be given precedence over Sabin's oral vaccine." In contrast, the following year, 1963, Sabin's polio vaccine was licensed in Italy and made mandatory in 1966.

The Cutter Incident

In 1955 Cutter Laboratories was one of several pharmaceutical companies licensed by the U.S. government to produce the Salk polio vaccine. In what became infamously known as the Cutter Incident, a manufacturing error resulted in a large quantity of Cutter vaccines contaminated with the live virus. It was one of the worst pharmaceutical disasters in U.S. history and caused several thousand children to be exposed to the polio virus, resulting in 56 cases of paralysis and five deaths.

In the years after his discovery, many supporters, particularly the National Foundation, "helped him build his own dream of founding a research complex to study biological phenomena "from the cell to society." The Salk Institute for Biological Studies was opened in 1963 in La Jolla, California, near San Diego. Salk was convinced that the institution would help new and emerging scientists, and in 1966 he described his "ambitious plan to create a kind of Socratic Academy in which scientific and humanistic cultures, seemingly separate from each other, would find a climate conducive to cross-development." The New York Times, in a 1980 article celebrating the 25th anniversary of the Salk vaccine, described operations at the facility as follows:

At the institute, a magnificent complex of laboratories and study units that sits on a cliff overlooking the Pacific, Dr. Salk holds the titles of founder, director and internal member. His laboratory group deals with the immunological aspects of cancer and the mechanisms of action of autoimmune diseases, such as multiple sclerosis, in which the immune system attacks the body's own tissues.

In an interview about his future hopes for the institute, Salk says, "At the end of the day, what may be most relevant is my founding of this center and all that will come out of it, in that it is an example of a place of excellence, a creative environment for creative minds." Francis Crick, co-discoverer of the DNA molecule, taught at the Salk Institute until his death in 2004.

A vaccine for AIDS

Beginning in the mid-1980s, Salk also worked to develop a vaccine for another, more recent scourge, AIDS. To promote such research, he became the co-founder of the Immune Response Corporation along with Kevin Kimberlin and patented Remune, a therapy that acted directly on the immune system. The project for an AIDS vaccine was halted in 2007, twelve years after Jonas Salk's death in 1995. Although much progress had been made in the treatment of AIDS, "the world was still waiting for the miracle vaccine the polio conqueror had sought."

In 1966 the New York Times, referring to Dr. Salk, called him "the Father of Biophilosophy." According to Times columnist Howard Taubman, "He never forgets that there is still a vast darkness that man must penetrate. As a biologist, he believes that his science is a new frontier for extraordinary discoveries; as a philosopher, he is convinced that humanists and artists have joined scientists in reaching a degree of understanding of human beings in all their physical, mental and spiritual complexity. Such interchanges could lead, and Salk hopes, to a new and important school of thinkers, to be designated as biophilosophers." Salk describes his "biophilosophy" as the application of a "biological and evolutionary point of view to philosophical, cultural, social and psychological problems." He elaborates on this topic in two of his books, Man's Unfolding and The Survival of the Wisest. In a 1980 interview, he also laid out his belief that, in the future, a sharp increase and predictable leveling off in world population would lead to a change in human attitudes:

I think biological concepts provide useful analogies for understanding the nature of humans. People think of biology as practical matters such as drugs, but its contribution to our knowledge of living systems and ourselves will be equally important. In past ages, man dealt with death, the high mortality rate; his attitudes were anti-death and anti-disease. In the future, they will be expressed in terms of pro-life and pro-health. The past was dominated by death control; in the future, birth control will be more important. The changes we are observing are part of a natural order and test our ability to adapt. It is very important to cooperate and collaborate. We are, together with nature, the co-authors of our destiny."

His definition of a "biophilosopher" is "someone who draws on the sacred scriptures of Nature, recognizing that we are the product of the process of evolution, and understands that we have become the process itself, due to the emergence and evolution of our consciousness, our awareness, our ability to imagine and anticipate the future and to choose among multiple alternatives."

The day after his graduation from medical school, Jonas Salk married Donna Lindsay, a candidate director of the New York College of Social Work. David Oshinsky writes that her father, Elmer Lindsay, "a wealthy Manhattan dentist, considered Salk socially far inferior to all of Donna's former suitors." Eventually, the man agreed to the marriage on two conditions: first, Salk would have to wait until the title Medicinæ Doctor (M.D.) could be placed before his name on the wedding invitations, and then he would have to improve his "rather pedestrian status" by giving himself a middle name. Jonas and Donna had three sons, Peter, Darrell, and Jonathan Salk. In 1968 they divorced, and in 1970 Salk married Françoise Gilot, a former lover of Pablo Picasso. Jonas Salk died of heart failure on June 23, 1995, at age 80, in La Jolla, and was buried in El Camino Memorial Park, San Diego.


  1. Jonas Salk
  2. Jonas Salk
  3. ^ a b Rose DR (2004). "Fact Sheet - Polio Vaccine Field Trial of 1954". March of Dimes Archives. 2004 02 11.
  4. ^ Bookchin, Debbie, and Schumacher, Jim. The Virus and the Vaccine, Macmillan (2004) ISBN 0-312-34272-1
  5. ^ a b Oshinsky, p.96.
  6. ^ a b "The Real Reason Why Salk Refused to Patent the Polio Vaccine". Retrieved July 14, 2014.
  7. ^ Jacobs, Charlotte DeCroes. "Vaccinations have always been controversial in America: Column", USA Today, August 4, 2015
  8. ^ Charlotte DeCroes Jacobs (April 21, 2015). Jonas Salk: A Life. Oxford University Press. pp. 45–. ISBN 978-0-19-933443-8.
  9. ^ Roberts, Sam (July 27, 2012). "New York Census Data, Centuries Old, Is Now Online".
  10. ^ City College of New York Microcosm Yearbook, 1934
  11. Bookchin S. 25
  12. Oshinsky, p. 100
  13. Oshinsky S. 101
  14. Bookchin S. 26
  15. Jonas Salk, pag. 1500 - Grande Enciclopédia Universal - edição de 1980 - ed. Amazonas
  16. Denenberg, Dennis, and Roscoe, Lorraine. 50 American Heroes Every Kid Should Meet Millbrook Press (2006)
  17. «Criador da vacina contra a pólio morre aos 80 nos EUA». Folha de São Paulo. 24 de junho de 1995. Consultado em 19 de março de 2021
  18. Bankston, John (2002). Jonas Salk and the Polio Vaccine. Bear, Delaware: Mitchell Lane Publishers. pp. 30–32
  19. McPherson, Stephanie (2002). Jonas Salk: Conquering Polio. Minneapolis, Minnesota: Lerner Publications Company. pp. 33–37

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