The Persistent Misleading Claim That Vaccines Aren't Properly Tested for Safety

It's a common, misleading refrain in anti-vaccine circles: Childhood vaccines may be unsafe because few if any have been tested in placebo-controlled trials before being approved. But that claim misunderstands the vaccine safety testing process and takes advantage of a narrow definition of a placebo, scientists told us.

"Not a single childhood vaccine on the schedule has ever been through a double-blind placebo-based trial prior to licensure," Del Bigtree, a prominent activist with ties to Health and Human Services Secretary Robert F. Kennedy Jr., said at a March 9 conference that billed itself as being about a "massive epidemic" of vaccine harm. "It is now a known fact they were never done. No placebo trial anywhere in sight," Bigtree went on to say.

Kennedy has been making similar claims for years. He previously led Children's Health Defense, a group that says its "mission is ending childhood health epidemics by eliminating toxic exposures" and writes frequently about alleged harms from vaccines, and hired Bigtree as his communications director during his 2024 presidential run. Kennedy has generally refrained from speaking about vaccines in recent months, but in a congressional hearing on April 21, he repeated the claim when stating that he's "never been anti-vax."