What Kennedy has said about the polio vaccine in recent years

Robert F. Kennedy Jr. began a tour of Capitol Hill this week to pay courtesy calls on senators who will vote on his nomination to be health secretary and to calm concerns that he would limit access to vaccines, especially for polio. “I’m all for the polio vaccine,” Kennedy said to a throng of reporters on Monday.

President-elect Donald Trump also sought to head off inevitable questions.

“You’re not going to lose the polio vaccine,” Trump declared during a news conference Monday. “That’s not going to happen.”

But a New York Times review of Kennedy’s public comments over the past several years shows that he has consistently expressed views about the polio vaccine that are at odds with the medical consensus. For example, he has suggested that after the vaccine was first introduced, it might have caused a wave of cancers “that killed many, many, many, many, many more people than polio ever did.” And he has said the idea that the vaccine resulted in a drastic decline in polio cases is “a mythology” that is “just not true.”

His opinions on the polio vaccine have come under scrutiny since an article in The New York Times reported Friday that Aaron Siri, a lawyer who is advising Kennedy during the transition, had filed petitions on behalf of a nonprofit to revoke federal approval of the stand-alone polio vaccine, known as IPOL, and to pause distribution of 13 other shots, some of which include polio immunization.

Kennedy’s spokesperson, Katie Miller, also weighed in Monday in an email message: “Mr. Kennedy believes the polio vaccine should be available to the public and thoroughly and properly studied.”

Here is an analysis of some of Kennedy’s statements about the polio vaccine.

On the polio vaccine’s effectiveness

On a podcast posted on July 6, 2023, with computer scientist Lex Fridman, Kennedy said that “there’s no vaccine that is, you know, safe and effective,” a statement he later walked back. Fridman challenged him: “Those are big words. What about polio?”

Kennedy, now 70, said the polio vaccine contained a virus called Simian Virus 40, or SV40, and claimed that it had caused an explosion of soft-tissue cancers among people of his generation “that killed many, many, many, many, many more people than polio ever did.”

He was referring to the period from 1955 to 1963, when some of the polio vaccine was contaminated with the virus, which came from the monkey cell cultures used to produce the vaccine.

Kennedy elaborated: “So if you say to me, Was the polio vaccine effective against polio? I’m going to say yes. If you say to me, Did it cause more deaths than it averted? I would say, I don’t know, because we don’t have the data on that.”

A review by the Institute of Medicine in 2003 concluded that “the evidence is inadequate to accept or reject a causal relationship between SV40-containing polio vaccines and cancer.”

Dr. Paul Offit, a vaccine expert at the Children’s Hospital of Philadelphia, said in an email that the question was carefully examined after researchers learned that it had caused cancer when injected into rodents.

But scientists were reassured, Offit said, to learn that the simian virus was killed in the injectable polio vaccine by the same process used to inactivate the polio virus. For the oral polio dose, the simian virus was killed in the digestive tract, Offit said.

By the late 1990s, a large study was published that followed people who were likely to have been exposed to the monkey virus 30 years earlier and compared their cancer rates to those who had not been exposed. The study concluded that the virus-contaminated vaccine was not associated with an increased rate of numerous cancers.

The vaccine’s impact on the decline in U.S. cases

In a debate with Alan Dershowitz, the retired Harvard University law professor, posted Sept. 3, 2020, and in another podcast in 2024, Kennedy pushed back on the epidemiology of how polio immunization had driven down rates of polio and related deaths.

“The proposition and the theology that smallpox and polio were abolished due to vaccination is controversial,” Kennedy said in 2020. “That is not a proposition that is universally accepted.”

Citing a study published in the journal Pediatrics in 2000, Kennedy asserted that the decline in deaths from infectious diseases “during the first half of the 20th century had virtually nothing to do with vaccines.” He added: “It had everything to do with sanitation, with hygiene, electric refrigerators, with reduction in population densities.”

But those developments occurred before the polio vaccine came to market in 1955. The study also reported “impressive” reductions in diphtheria, measles, whooping cough, tetanus and polio, saying deaths from those diseases had been “virtually eliminated” once vaccines became widely available.

In another podcast, taped in 2019 and released in 2023, Kennedy cast doubt on the idea that vaccines have wiped out infectious disease. “I know it’s a mythology to say that it cured polio and smallpox and measles, et cetera, but it’s just not true,” he said.

For polio specifically, the Centers for Disease Control and Prevention have reported steep declines in case counts and deaths since the first vaccine was licensed in 1955. Around 1952, about 16,000 cases and 1,879 deaths were reported each year. That fell to fewer than 1,000 cases by 1962 and then lower, to 100 cases per year, according to the CDC report.

By 1979, the polio virus circulating in the environment was eradicated from the United States. But the oral polio vaccine in use at that time contained a weakened, but live, form of the polio virus, and it caused 8 to 10 cases of paralytic polio each year. In 1999, federal regulators addressed the issue by replacing it with the current standalone vaccine containing the inactive virus.

“That polio disappeared without a vaccine is just wrong,” said Dr. Walter Orenstein, who ran immunization programs for the CDC in the late 1980s and 1990s.

Vaccine risks for infants and young children

Kennedy has also cited polio vaccines in his broader argument that there is no proof that any vaccine carries more benefit than harm. He narrowed in on certain studies with short periods of safety follow-up, including one for the current standalone polio vaccine.

“Nobody knows the risk profile for any vaccine that is currently on the schedule,” he said in the debate with Dershowitz. (He was referring to the CDC’s recommendations that vaccines be given to infants and young children at certain ages.) “That means nobody can say with any scientific certainty that that vaccine is averting more injuries and deaths than it is causing.”

Some researchers argue that more funding is needed to study the safety of vaccines. As it stands, federal officials scan databases for signs of vaccine concerns on a day-to-day basis, according to Dr. Sean O’Leary, a professor of pediatrics and infectious diseases at the University of Colorado Anschutz Medical Campus.

O’Leary, a liaison to the CDC for the American Academy of Pediatrics, said officials monitor a large database where the public, doctors and vaccine makers can report vaccine side effects. When unexpected trends occur, they can look for a larger problem in other databases available in the United States and consult with vaccine safety scientists who use similar data in Europe.

“I think it’s a mistake to say that we have not been monitoring vaccine safety, because the U.S. absolutely has,” O’Leary said. “What we’re seeing with some of the these claims is a classic anti-vaccine tactic where they sort of cherry-pick specific studies or specific issues and then try and say, ‘Look, this is evidence that the vaccine isn’t safe.’”

This article originally appeared in The New York Times.

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