HHS Secretary RFK Jr. tussled with Sen. Chris Murphy about measles vaccine safety. Who was right?

Health Secretary Robert F. Kennedy Jr.’s comments about the measles vaccine briefly took center stage during his May 14 Senate testimony. 

Kennedy appeared before the Health, Education, Labor and Pensions Committee to discuss Health and Human Services’ 2026 budget, and senators questioned him about the 2025 measles outbreak that has killed three people, including two children. 

Sen. Chris Murphy, D-Conn., questioned Kennedy’s statements about the measles vaccine. 

"You have consistently been undermining the measles vaccine," Murphy said. "You told the public that the vaccine wanes very quickly. You went on the ‘Dr. Phil’ show and said that the measles vaccine was never fully tested for safety. You said there’s fetal debris in the measles vaccine."

Kennedy answered, "All true. All true."

Murphy tried to point to Kennedy’s remarks from his testimony earlier the same day, but Kennedy interrupted:

Murphy: "This morning, in front of — "

Kennedy: "Do you want me to lie to the public?"

Murphy: "That’s not — None of that is true." 

Kennedy: "Of course it’s true."

Before becoming the nation’s top public health official, Kennedy notched two decades of work as a leader in the antivaccine movement. 

Kennedy’s inaccurate statements mischaracterize how the measles vaccine is made, how it was tested and how it works. Infectious disease and vaccine experts told PolitiFact that the two-dose MMR vaccine provides lifelong protection; that scientists safety tested it before it was approved for use; and that it does not contain human fetal cells or whole fetal DNA. 

We contacted HHS and received no response. 

Measles vaccination provides lifelong protection, doctors and vaccine experts say

In early April, Kennedy told CBS News that measles persists because the vaccine’s effectiveness decreases fast. "We’re always going to have measles, no matter what happens, because the vaccine wanes very quickly," he said. 

That’s inaccurate, vaccine experts said. 

The measles vaccine is part of a combination vaccine known as the measles, mumps and rubella vaccine, or the MMR vaccine. It also can include the varicella vaccine, called the MMRV vaccine. 

Two infectious disease doctors and a vaccinology professor told PolitiFact that when people receive the measles vaccine’s recommended two doses, it provides strong, long-lasting protection against measles infection.  

"You will have about a 97% chance of being protected and that protection will extend lifelong," said Dr. William Schaffner, infectious disease professor at Vanderbilt University Medical Center.

That matches what the Centers for Disease Control and Prevention — an agency Kennedy oversees — says about the measles vaccine’s efficacy. 

The MMR’s measles vaccine "provides one of our most remarkably durable and long-lasting protective vaccine-induced antibodies," said Patsy Stinchfield, a retired pediatric nurse practitioner and the immediate past president of the National Foundation for Infectious Diseases.

Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, said measles immunity doesn’t wane because measles is a long-incubation period disease, which means it can take up to 21 days to develop symptoms after exposure. 

Measles antibodies might decrease over time, but that doesn’t mean a person’s vaccine-induced protection against measles infection is waning, experts said. 

To be protected against disease, "all you need is immunological memory cells," Offit said. When you’re exposed to the virus, there’s plenty of time for those memory cells to become activated and trigger the immune system to make measles antibodies, he said. 

For other diseases covered by the MMR vaccine, the protection can wane over time, said Paulo Verardi, a University of Connecticut virology and vaccinology professor. That’s true of mumps immunity, for example, so people who got vaccinated as children might be less protected from infection as adults, he said. But the measles vaccine doesn’t have that issue, he said.

"It is rare for someone who has been vaccinated to get measles, and if they do, it is usually a mild case," Verardi said. "Most outbreaks happen not because the vaccine wears off quickly, but because not enough people are vaccinated."

Measles vaccine was safety tested before licensure 

During a town hall hosted by TV personality Phil McGraw, known as Dr. Phil, Kennedy said, "The measles vaccine works," and said HHS recommends vaccination against measles. But there are "problems" with the vaccine, Kennedy added.

"The problem is — it’s really with the mumps portion of the vaccine and the combination — and it was never safety tested," he said. "That combination was never safety tested, and people just assumed that, you know, if the three separate vaccines were safe, then when you combined them they would be safe. But we now know there’s some viral interference."  

Varardi said U.S. regulators approved the first combined MMR vaccine in 1971 "after extensive clinical testing to make sure it was safe and worked well." 

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Kennedy also often talks about testing vaccines against placebos — inactive substances that provide no protection against disease — and HHS recently announced potential changes to vaccine testing that would require placebo testing.

When the MMR vaccine was combined, research had shown that each of the components was safe and effective individually, and it isn’t always ethical to test them against placebos that would leave test subjects unprotected from infection, Offit said. 

Fortunately, Offit said, we have "about 50 years of data" on the billions of doses of the MMR vaccine that have been administered. 

Schaffner said scientists continue to monitor the MMR vaccine’s safety. Ongoing vaccine safety surveillance is important to catch extremely rare side effects. 

A Finland MMR vaccine study found that 5.3 in every 100,000 people vaccinated experienced serious adverse reactions. A 2021 study found that among 12,032 vaccinated people, four people reported serious vaccine-related events. 

No, the MMR vaccine doesn’t contain human fetal cells

During an April 30 News Nation interview, Kennedy said some people "have religious objections to the vaccination, because the MMR vaccine contains a lot of aborted fetus debris and DNA particles, so they don't want to take it."

The MMR vaccine contains weakened live viruses, and viruses must be grown in cells. 

The measles and mumps viruses are grown in chicken embryo cells and the rubella virus is grown in human fetal cells, which first came from an elective abortion performed in the early 1960s and have been replicated in labs and used to manufacture vaccines for decades. 

Before it becomes a vaccine component, the virus is extracted from the cells where it is grown and then it is weakened and treated with an enzyme that fragments any remaining DNA, Offit said. 

So, does the MMR vaccine contain "fetal debris," fetal cells or whole fetal DNA? No, said Offit and Varardi. 

Whatever DNA is present from the original cell line used to grow the virus likely could be measured in picograms, "meaning trillionths of a gram," Offit said.

The origin of the cells used to grow the virus has historically sparked religious concerns. Religious leaders including the Catholic Pontifical Academy for Life concluded that it is both morally permissible and responsible to use the vaccine, the Catholic News Agency reported. 

Our ruling

Kennedy told Murphy that it’s "all true" that the measles vaccine wanes quickly, was never fully tested for safety and contains fetal debris. 

Scientists say the measles vaccine offers lifelong protection that is 97% effective at preventing the virus. Scientists tested the MMR vaccine before it was approved for use and perform ongoing safety surveillance research; studies show that serious adverse effects are rare. 

Finally, the MMR vaccine may contain trace amounts of fragmented DNA, but it does not contain whole fetal cells or fetal DNA. 

We rate Kennedy’s statement False. 

PolitiFact Researcher Caryn Baird contributed to this report.

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