Editor’s note: This piece has been updated with a response from Robert F. Kennedy Jr.’s campaign.
On July 10, Fox News anchor Jesse Watters pressed Democratic presidential candidate Robert F. Kennedy Jr. on his claims about vaccine safety. Kennedy argued that vaccines “should have the same kind of testing—placebo-controlled trials—that we have for every other medication” and alleged that “vaccines are exempt from pre-licensing controlled placebo trials.” This claim is missing context.
Placebo trials are a standard feature of the third phase of clinical trials for new vaccines, which are “generally given to thousands of people, with those who receive the vaccine compared to those who receive a placebo,” according to the Food and Drug Administration (FDA).
Some previously authorized vaccines do not undergo placebo trials when redeveloped. Prevnar 13, for example, is a standard infant immunization that has not undergone placebo controlled trials. Prevnar 7, its predecessor, was licensed for public consumption in 2000.
The World Health Organization published a report in 2014 citing “ethical concerns” over the use of placebo trials in cases where “participants in the control arm are deprived of an existing vaccine,” recommending such trials only in certain circumstances. This does not, however, contradict the fact that placebo controlled trials are a standard part of the vaccine licensing process.
Kennedy’s claim appears to hinge on his definition of “placebo.” Informed Consent Action Network (ICAN), an anti-vaccine advocacy group for which Kennedy has served as legal counsel, has cited a CDC guideline saying that a placebo is a “substance or treatment that has no effect on living beings” to argue that only water or saline are acceptable placebos.
As Dr. Paul Offit, a professor of vaccinology at the University of Pennsylvania, writes, the FDA, as the vaccine regulator, has final authority on the definition of a placebo for vaccine trials. The FDA’s approved definition of a placebo is an “inactive” or “inert” substance that produces no immune response. This definition includes but is not limited to water-based substances, and includes placebos with sugar or starch components.
“The only way I would interpret [Kennedy’s comments] is in terms of how he would define a placebo,” Offit tells The Dispatch. “But he’s made up his own definition of what a placebo is.”
Update: In response to a request for comment following the statement, the Kennedy campaign team told The Dispatch Fact Check that placebos for vaccine trials are “almost never inert” because the FDA allows previously authorized vaccines to be used in control trials, as well as adjuvants—substances designed to enhance the effect of a control substance.
In such trials, the FDA allows those older approved vaccines to be used as a “control substance” to track adverse changes in the new product. Such substances are not inert.
Dr. Offit tells The Dispatch that these further claims are misleading. The adverse effects of previously authorized vaccines are already captured at the population level, for example through the Vaccine Adverse Event Reporting System.
Nor do adjuvant substances, such as aluminum, produce an immune response unless they are combined with a non-inert substance. “The adjuvant itself doesn’t enhance the immune response to something that isn’t immunogenic,” he says. “If I gave you an aluminum salt, which is an adjuvant, and I combined it with sucrose, it’s not going to create an immune response to sucrose, because that’s an immunologically inert substance.”
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