The US Department of Health and Human Services said it will require that all new vaccines be tested in placebo-controlled trials before they’re licensed for use, raising urgent questions about the system used to clear updated Covid-19 boosters each respiratory virus season.
“Under Secretary Kennedy’s leadership, all new vaccines will undergo safety testing in placebo-controlled trials prior to licensure — a radical departure from past practices,” HHS said in a statement Wednesday.
Covid-19 vaccines, first cleared by the US Food and Drug Administration in late 2020, have been updated each year in a system similar to that used for flu vaccines, so they can better target circulating strains of the virus. The vaccine constructs remain the same each year, but the version of the virus they protect against can be tweaked. The FDA typically selects strains for the updated vaccines in June so they can be ready for distribution by the fall.
Experts warn that requiring placebo-controlled trials before clearing new versions – which could involve enrolling participants, giving some the vaccine and some a placebo shot, and waiting some period of time to assess safety and efficacy – would delay availability of updated Covid shots by months, putting vulnerable people at risk.
“The advantage of updating the vaccine every year to make it more close to the circulating strain is, you get better antibody responses, so for four to six months,you will clearly have better protection against mild to moderate disease, and that matters especially for people who are more frail,” particularly people 75 and older, said Dr. Paul Offit, a vaccine scientist at the Children’s Hospital of Philadelphia.
Novavax later said the FDA had requested a “postmarketing commitment” for a clinical trial, suggesting that a study would be required of the vaccine after it received full approval (it had been available through emergency use authorization since 2022). HHS’s newest statement adds to questions about whether a trial would be required before approval, not just for Novavax’s vaccine but also for updated versions of those from Moderna and Pfizer.
Experts said that if that’s the case, it would signal a new standard for Covid vaccines.
“FDA clearly, after a deliberative process, adopted an approach that treated Covid-19 vaccine boosters like influenza boosters, not like a new product, and held to that over a few years,” said Dorit Reiss, a professor of law at UC Law San Francisco. “They adopted a standard, and now they’re changing it.”
Although Covid-19 has become less deadly since the height of the pandemic as the population developed widespread immunity through both infection and vaccination, the virus still kills and can be especially dangerous for the elderly. Between September 2023 and August 2024, there were more than 36,000 deaths from Covid-19 among people 65 and older, CDC data showed.
In its statement Wednesday, HHS also claimed that current systems for monitoring vaccine safety, including the Vaccine Adverse Event Reporting System and the Vaccine Safety Datalink, don’t capture vaccine injuries sufficiently and “have become templates of regulatory malpractice.” HHS said it’s building surveillance systems now “that will accurately measure vaccine risks as well as benefits.”
Offit, who co-invented a rotavirus vaccine and serves on the FDA’s independentpanel of vaccine advisers, said the assertion that those systems are inadequate is false.
“Where’s the evidence for that?” he asked. “I would argue all the evidence is on the other side.”
He pointed out that within weeks, the systems picked up very rare side effects such as myocarditis, or inflammation of the heart muscle, that happened in about 1 in 50,000 people who received mRNA Covid-19 vaccines and rare blood clots in people who received a now-discontinued vaccine using a different technology from Johnson & Johnson that affected about 1 in 250,000.
“That’s very good,” he said. “This sort of notion that people have lost faith in vaccines because of the lack of safety surveillance systems is wrong.”