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.

New rules implemented by Health and Human Services Secretary Robert F. Kennedy Jr. will require updated existing vaccines to undergo the same testing as completely new vaccines, which could add months of delay to production.

“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,” the Department of Health and Human Services (HHS) said in a statement to CNN.

A Department of Health and Human Services spokesperson called the move "a radical departure from past practices."

The top US health department plans to require placebo testing for all vaccines in an effort to offer "straightforward" public health information, but experts say such testing could limit availability and raise ethical concerns.

A major change in the way HHS plans to evaluate vaccine safety is raising fears that approvals will become unnecessarily onerous and make shots for COVID-19 and other viruses scarcer. Why it matters: The change under Secretary Robert F.