Robert F. Kennedy Jr. Should Stop Talking About Vaccines

The presidential candidate now claims that the polio vaccine killed more people than it saved.

Robert F. Kennedy Jr. was born on January 17, 1954. At the time of his birth, polio paralyzed as many as 50,000 children every year and killed 1,500. The year of RFK Jr.’s birth also marked the start of the trial of Jonas Salk’s polio vaccine, which was available in 1955. In the early 1960s, Salk’s inactivated polio vaccine was replaced by Albert Sabin’s live, weakened viral vaccine. By 1979, polio had been eliminated from the United States. RFK Jr.’s first child was born in 1984; five more would follow. Unlike his parents, RFK Jr. didn’t have to worry that his children might be paralyzed by polio. 

On July 6, 2023, RFK Jr. appeared on Lex Fridman’s podcast, which boasts more than 3 million listeners. RFK Jr. declared, “There is no vaccine that is safe and effective.” Fridman, trying to select a vaccine that everyone in RFK Jr.’s generation would have appreciated, countered, “Can we talk about polio?” “Well, here’s the problem,” said Kennedy, “The polio vaccine contained a virus called SV40. It’s one of the most carcinogenic viruses known to man…98 million people who got that vaccine in my generation now have this explosion in soft tissue cancers [that] kill many, many, many, many, many, many more people than polio ever did.” RFK Jr. was referring to a scare surrounding polio vaccines in the early 1960s that didn’t pan out.

Here's what happened. Both Jonas Salk and Albert Sabin used monkey kidney cells to grow polio viruses for their vaccines. At the time, 39 monkey viruses had been identified. Salk and Sabin’s vaccines led to the discovery of the 40^th. It was called SV40 (Simian Virus 40). Dr. William Mann, then director of the National Zoo in Washington, D.C., explained how the monkeys came to be infected. “The monkeys were trapped in Africa and off-loaded at airports where they would share their viruses,” he said. “They would all be forced together in small spaces, sharing their urine and feces…It was a real mess.”

Maurice Hilleman, a researcher at Merck, was the first to discover that both Salk’s and Sabin’s polio vaccines contained SV40. Hilleman then performed an experiment that terrified public health officials and, within several years, made SV40 one of the most studied viruses in the world. Hilleman injected SV40 into newborn hamsters, finding that ninety percent developed tumors under their skin as well as in their lungs, kidneys, and brains. At the time of Hilleman’s discovery, Salk’s vaccine had been injected into tens of millions of Americans. Sabin’s vaccine hadn’t yet been licensed in the United States, but it had been given to more than 90 million people in Russia.

During the next few years, studies of SV40 were reassuring. To make his vaccine, Salk had inactivated polio virus with formaldehyde, which also inactivated SV40. Further, researchers found that although SV40 caused cancer when it was injected into hamsters, it didn’t cause cancer when it was fed to hamsters. Sabin’s vaccine was swallowed, not injected. And none of the children inoculated with Sabin’s vaccine developed antibodies to SV40. Apparently, the virus just passed through the intestines without causing an infection. Researchers then compared cancer rates in children who had received SV40-containing polio vaccines with unvaccinated children. Eight years after receiving the tainted vaccines, the cancer incidence was the same in both groups. The same was true fifteen and thirty-five years later. And it was true for children who received SV40-contaminated vaccines in the United States, the United Kingdom, Germany, and Sweden. By the mid-1990s public-health officials were confident that the inadvertent contamination of polio vaccines with SV40 in the early 1960s hadn’t caused cancer.

The false claim that polio vaccines caused cancers has now been put to rest. Toward the end of the Lex Fridman podcast, RFK Jr. said, “There are many times that I found that I've made mistakes, and we correct those mistakes.” More than a dozen studies have shown that the SV40-contaminated polio vaccines in the late 1950s and early 1960s never caused cancer in people. Now is your chance, Mr. Kennedy, to correct yet another of your false claims about vaccines.