RFK Jr. repeats false claim that MMR vaccine contains fetal tissue

The health secretary's inaccurate claim stems from a misunderstanding of how the measles, mumps and rubella vaccine is made. Published Aug. 31, 2026 Claim: The vaccine for measles, mumps and rubella contains tissue from aborted fetuses, as U.S. Health Secretary Robert F. Kennedy, Jr. claimed in August 2026. Rating: In August 2026, U.S. Health Secretary Robert F. Kennedy Jr. claimed in an X post that the vaccine used to prevent measles, mumps and rubella contained "fetal tissue." Kennedy was responding to Pennsylvania Gov. Josh Shapiro, a Democrat, who accused him of peddling conspiracy theories about vaccines. In his X post on Aug. 25, Kennedy defended his claim (archived). He said, in part: The rubella virus used in MMR-II is grown on the cultured cell line composed of lung tissue from an aborted three-month-old female embryo and listed as "WI-38 human diploid lung fibroblasts" in the ingredients of MMR-II as portions of these cells end up in each vial of MMR II. This was not the first time Kennedy made this claim. On April 30, 2025, he claimed during a NewsNation townhall with television presenter Chris Cuomo that the MMR vaccine "contains a lot of aborted fetus debris" (starting at the 1:08 mark). However, the health secretary's claim that the vaccine contains fetal material from abortions was incorrect. Therefore, we have rated the claim false. The 2025 measles outbreak It is true that, in 2025 and 2026, the U.S. was seeing its worst outbreak of measles since 1991, according to the Centers for Disease Control and Prevention, with 2,777 cases from the beginning of 2026 to Aug. 20, 7% of which required hospitalization. As of this writing, the CDC has also reported three deaths in 2025 and none in 2026. (Centers for Disease Control and Prevention) (CDC) Measles is a highly contagious disease that requires 95% of the population to be immunized to prevent its spread, according to Harvard Medical School. For years, the country was able to prevent new cases by keeping the vaccination rates at or above 95%. However, in more recent years, the vaccination rate began to fall. It was at 92% in 2023 and at 82% in the area where the 2025 outbreak started in West Texas, also according to Harvard Medical School. Experts have long identified disinformation and misinformation as key forces causing fears about the safety of the MMR vaccine and others, and, as Snopes reported in February 2024 and in May 2017, Kennedy has been a prominent voice in promulgating false claims about vaccines. For full immunization, the schedule calls for two doses of the MMR vaccine, according to the CDC. Most people who were infected in the 2025 and 2026 measles outbreak were either unvaccinated, had an unknown vaccination status or had received only one of the two doses, according to Harvard Medical School. False claims about the MMR vaccine The MMR vaccine has long been the target of false claims. For example, a now-debunked article, reported on by Snopes in January 2019, succeeded in convincing many concerned parents that a mercury-based preservative known as thimerosal, which some vaccines and other injections used to contain, was responsible for an increase in autism rates. While it is true that autism diagnoses have continued to increase in the U.S., it is not for this reason. In fact, childhood vaccines no longer contain thimerosal. The combined MMR jab contains three live attenuated viruses. These versions of the viruses are too weak to cause an infection but are strong enough to provoke an immune reaction in which the body produces specific antibodies to fight the viruses if the person is exposed to them later. The claim that the MMR vaccine contains fetal material stems from a misunderstanding of how the rubella attenuated virus is produced. According to an article that appeared in the Jan. 29, 2020, issue of the medical journal Vaccine, the most common rubella strain used in vaccines is attenuated in a cell culture that uses the specific cell line WI-38: The most commonly used vaccine strain for the rubella virus is attenuated strain RA27/3, which was extracted using explant liver culture and attenuated by passaging in human diploid fibroblasts (WI-38), at temperatures of 30 °C and 35 °C. The cell line WI-38 was isolated "from the lung tissue of a 3-month-old, female, embryo," according to the description of a website that commercializes the cells for use in vaccine development. eonard Hayflick, a U.S. scientist, isolated the cells from the embryo of a legal abortion in Sweden in the early 1960s. The cell line is credited with preserving countless lives, according to a 2024 obituary for Hayflick in the journal NPJ Aging (emphasis ours): The 'Hayflick cells', WI-38, have been the basis for producing vaccines for poliomyelitis, measles, mumps, rubella, varicella, adenovirus, rabies, and hepatitis A. Over the last 50 years, the number of people benefiting from these vaccines has been estimated to be several billion worldwide. However, vaccine development has not needed to take new cells from more recent abortions. Further, while vaccine developers do attenuate the virus in the cells, they later extract it and purify it, removing all trace of WI-38 cells. In sum, no trace of the cells appears in the vaccine. Sources CDC. "Measles Cases and Outbreaks." Measles (Rubeola), 1 May 2024, www.cdc.gov/measles/data-research/. Accessed 9 May 2025.---. "Measles Vaccination." Measles (Rubeola), 17 Jan. 2025, www.cdc.gov/measles/vaccines/index.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fvaccines%2Fvpd%2Fmmr%2Fpublic%2Findex.html. Accessed 9 May 2025.Christensen, Laerke. "Trump Claimed Autism Rates Are Rising. Here Are the Facts." Snopes, Snopes.com, 8 Mar. 2025, www.snopes.com/news/2025/03/09/trump-autism-rates-facts/. Accessed 9 May 2025.Dubé, Ève, et al. "Vaccine Hesitancy, Acceptance, and Anti-Vaccination: Trends and Future Prospects for Public Health." Annual Review of Public Health, vol. 42, no. 1, Apr. 2021, pp. 175–91, https://doi.org/10.1146/annurev-publhealth-090419-102240.Gorvett, Zaria. "The Controversial Cells That Saved 10 Million Lives." BBC, 4 Nov. 2020, www.bbc.com/future/article/20201103-the-controversial-cells-that-saved-10-million-lives. Accessed 9 May 2025.Hayflick, L., and P. S. Moorhead. "THE SERIAL CULTIVATION of HUMAN DIPLOID CELL STRAINS." Experimental Cell Research, vol. 25, no. 1, May 1961, pp. 6–7, cogforlife.org/Hayflick1961ExpCell.pdf. Accessed 9 May 2025."Human Cell Strains in Vaccine Development." Cpp-Hov.netlify.app, historyofvaccines.org/vaccines-101/how-are-vaccines-made/human-cell-strains-vaccine-development. Accessed 9 May 2025.'Immunization'. U.S. Department of Health and Human Services, https://www.hhs.gov/immunization/basics/types/index.html.Kasprak, Alex. "Did the Government Censor an Expert Witness Who Changed His View on Vaccines?" Snopes, Snopes.com, 21 Jan. 2019, www.snopes.com/news/2019/01/21/witness-view-vaccines-autism/. Accessed 9 May 2025.---. "FACT CHECK: Would Breaking a Vaccine Vial Necessitate Evacuating a Building?" Snopes, Snopes.com, 15 May 2017, www.snopes.com/fact-check/vaccine-vial-evacuating-building/. Accessed 9 May 2025.Krow-Lucal, Elisabeth. 'Measles, Mumps, Rubella Vaccine (PRIORIX): Recommendations of the Advisory Committee on Immunization Practices — United States, 2022'. MMWR. Morbidity and Mortality Weekly Report, vol. 71, 2022. www.cdc.gov, https://doi.org/10.15585/mmwr.mm7146a1.Leonard Hayflick (1928- ) | Embryo Project Encyclopedia. https://embryo.asu.edu/pages/leonard-hayflick-1928. Accessed 9 May 2025.Mangtani, Punam, et al. "Safety Profile of Rubella Vaccine Administered to Pregnant Women: A Systematic Review of Pregnancy Related Adverse Events Following Immunisation, Including Congenital Rubella Syndrome and Congenital Rubella Infection in the Foetus or Infant." Vaccine, vol. 38, no. 5, Jan. 2020, pp. 963–78, https://doi.org/10.1016/j.vaccine.2019.11.070. Accessed 9 May 2025.Measles Rubella Vaccine - an Overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/immunology-and-microbiology/measles-rubella-vaccine. Accessed 9 May 2025.NewsNation. "RFK Jr.: Measles Cases in US Not as Bad as in Other Countries | CUOMO Town Hall: Trump's First 100 D." YouTube, 30 Apr. 2025, www.youtube.com/watch?v=w4i7kGh63jo. Accessed 9 May 2025.Q&A - DNA, FETAL CELLS & VACCINES: WHAT YOU SHOULD KNOW. Children's Hospital of Philadelphia Vaccine Education Center, Summer 2022, https://www.chop.edu/sites/default/files/vaccine-education-center-dna-fetal-cells-vaccines.pdf.Serrano, Manuel. "Leonard Hayflick (1928-2024) – Obituary." Npj Aging, vol. 10, no. 1, Springer Science and Business Media LLC, Oct. 2024, https://doi.org/10.1038/s41514-024-00174-0. Accessed 9 May 2025.Shmerling, Robert H. "Measles Is Making a Comeback: Can We Stop It? - Harvard Health." Harvard Health, 6 Mar. 2025, www.health.harvard.edu/blog/measles-is-making-a-comeback-can-we-stop-it-202503063091. Accessed 9 May 2025."Vaccine Ingredients: Fetal Cells." Chop.edu, 2024, www.chop.edu/vaccine-education-center/vaccine-safety/vaccine-ingredients/fetal-tissues. Accessed 9 May 2025.Vally, Hassan. 'The MMR Vaccine Doesn't Contain "Aborted Fetus Debris", as RFK Jr Has Claimed. Here's the Science'. The Conversation, 2 May 2025, http://theconversation.com/the-mmr-vaccine-doesnt-contain-aborted-fetus-debris-as-rfk-jr-has-claimed-heres-the-science-255718.West, Michael D., et al. "Leonard Hayflick (1928–2024)." Nature Aging, Nature Portfolio, Sept. 2024, https://doi.org/10.1038/s43587-024-00720-1. Accessed 9 May 2025.. Archived: https://archive.is/adlw1.WI-38 - CCL-75 | ATCC. https://www.atcc.org/products/ccl-75. Accessed 9 May 2025. By Anna Rascouët-Paz Anna Rascouët-Paz is based in Brooklyn, fluent in numerous languages and specializes in science and economic topics. Got tips? Reach out to her on Signal at rascouetsnopes.41 or via email at anna@snopes.com. Article Tags