RFK Jr. Says the MMR Vaccine Contains Fetal Tissue. It Doesn't.

Snopes traced the claim to a real but misunderstood manufacturing detail. The rubella strain in MMR-II is grown in a human cell line called WI-38, isolated in the early 1960s from the lung tissue of a fetus from a legal abortion in Sweden ^[1]. That much is true, and vaccine scientists don't dispute it — the obituary for the researcher who isolated the cells, Leonard Hayflick, credits WI-38 with helping produce vaccines that have saved an estimated several billion people from measles, mumps, rubella, polio and more ^[1].

What's false is that any of those original cells, or DNA from them, remain in the shot itself. After the weakened virus is grown inside WI-38 cells, manufacturers extract and purify it, filtering out everything else. "The virus is grown in these cells, then this virus is purified, meaning everything other than the virus is filtered out," one vaccine expert told reporters ^[3]. What trace genetic material survives purification is measured in "billionths or trillionths of a gram," according to Children's Hospital of Philadelphia's Vaccine Education Center ^[1] — nowhere near Kennedy's figure of 646 billion DNA fragments, and nowhere near intact "fetal tissue" or "debris." No new fetal cells have been harvested for vaccine production since WI-38 was established over 60 years ago ^[1].

This isn't a fringe social-media rumor — it's coming from the man who oversees U.S. vaccine policy. Shapiro says Kennedy went further in their private call, launching into what the governor called "a tirade" and "a rabbit hole of conspiracy theories and false claims" instead of discussing outbreak response ^[2]. Shapiro publicly countered that Kennedy's rhetoric is doing real damage: "Secretary Kennedy's actions to dismantle public health agencies and his language that undermines confidence in vetted medical guidance are contributing to these kinds of outbreaks" ^[2].

The claim is landing at a moment of genuine vulnerability. The U.S. is in the middle of its worst measles outbreak since 1991, with 2,777 cases logged nationally between the start of 2026 and Aug. 20 and three deaths recorded in 2025 ^[1]. Measles requires roughly 95% vaccination coverage to prevent spread, but national MMR rates have slipped from 97% in 2020 toward the low 90s, and to as low as 82% in the West Texas community where the current outbreak began ^{[1] [2]}.

Snopes rates the fetal-tissue claim false, and the underlying science backs that call: the manufacturing process removes the WI-38 cells before the vaccine is ever bottled, leaving no fetal tissue and no meaningful fetal DNA in the finished shot ^{[1] [3]}. That the nation's health secretary is repeating a long-debunked claim — one epidemiologists have linked to falling vaccination rates — while children are dying in an active outbreak is what makes this more than an internet rumor. It's official messaging shaping real vaccination decisions.