Health and Human Services Secretary Robert F. Kennedy Jr. will require new vaccines to undergo placebo testing, marking what a department spokesperson called “a radical departure from past practices.”
The policy change would force vaccines, in order to be approved for human use, to undergo studies in which half of individuals in a study receive a placebo – typically a saline shot – to compare results against the vaccine.
Placebo-controlled trials are already used to test new drugs or vaccines for safety and efficacy, but some experts consider it unethical to conduct such trials when a vaccine or treatment is already considered safe and efficacious. For example, they say, giving half of the kids in a trial a placebo for the measles vaccine when an already proven vaccine exists would put those participants unnecessarily at risk for the virus.
It remains unclear what HHS considers a “new” vaccine and whether that includes the flu and COVID vaccines, which are updated on an annual basis to better protect against currently circulating strains.
“FDA Commissioner Dr. Marty Makary has indicated that significant updates to existing vaccines—such as those addressing seasonal strain changes or antigenic drift—may be considered ‘new products’ requiring additional clinical evaluation,” the department spokesperson told ABC News.
Secretary of Health and Human Services Robert F. Kennedy Jr. speaks during a news conference on the FDA’s intent to phase out the use of petroleum-based synthetic dyes in the nation’s food supply, in Washington, April 22, 2025.
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But the spokesperson indicated the yearly flu vaccine might not be affected by the policy, calling it “tried and tested for more than 80 years.”
It appears, instead, that the policy could impact the rollout of future COVID vaccines, which are updated annually.
When asked to elaborate on what the department considers a “new” vaccine, the spokesperson said that federal health agencies would follow the “Gold Standard of Science”.
Kennedy has long questioned the safety of vaccines and argued that placebo-based trials are needed to ensure vaccines aren’t doing more harm than good.
Even as thousands were dying during the COVID-19 public health emergency, COVID vaccines still underwent placebo-controlled studies with more than 100,000 volunteers from diverse populations. Experts say the practice is necessary to determine if a vaccine is not only effective, but also safe.
A healthcare worker hands in surgical gloves pulling a COVID-19 vaccine liquid from a vial to vaccinate a patient.
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Many childhood vaccines were originally tested with placebo trials. Others have been available for decades, providing data from millions of people showing those vaccines are overwhelmingly safe and effective.
Once a vaccine for a disease is approved safe and effective, future versions of the shot are tested in clinical trials against the already approved shot. Clinical trials test whether the updated vaccines generate an immune response that’s comparable to or better than previous versions of the vaccine.
Even after vaccines are made available to the public, scientists continue to monitor them for safety. They also review any reports of side effects or reactions and share these facts with the public.