RFK Jr.’s Fetal-Tissue Claim About the MMR Vaccine Declared False

In August 2026, U.S. Health Secretary Robert F. Kennedy Jr. posted on X that the measles-mumps-rubella (MMR) vaccine “contains fetal tissue,” citing the WI-38 cell line derived from a three-month-old female embryo. Snopes evaluated the August 2026 claim and rated it false, noting that Kennedy’s description misrepresents how the vaccine is produced.

Snopes

The rubella component of MMR is attenuated using the human diploid fibroblast line WI-38, which was isolated in the early 1960s from lung tissue of a legally aborted embryo in Sweden by scientist Leonard Hayflick. The medical journal *Vaccine* (Jan. 29 2020) explains that the RA27/3 rubella strain is grown in WI-38 cells and then purified.

Snopes

The United States experienced its worst measles surge since 1991 during 2025-2026, with the CDC reporting 2,777 cases from the start of 2026 through Aug. 20 and a 7 % hospitalization rate. Harvard Medical School notes that vaccination coverage fell from 95 % (the herd-immunity threshold) to 92 % in 2023 and to 82 % in the West Texas region where the 2025 outbreak began. Most infected individuals were unvaccinated, had unknown status, or had received only one of the two recommended MMR doses.

Snopes

The CDC continues to endorse the two-dose MMR schedule and emphasizes that the vaccine contains three live attenuated viruses but no fetal material. Snopes’ fact-check underscores that Kennedy’s claim conflates the historical origin of the WI-38 cell line with the current composition of the vaccine, which is free of cellular remnants.

Snopes

Accurate information about vaccine composition is crucial for public confidence, especially amid declining immunization rates and a resurging measles outbreak. Mischaracterizing the role of a decades-old cell line can fuel vaccine hesitancy, potentially undermining herd immunity and prolonging the public-health crisis.

Snopes