COVID-19 vaccines work so well that most people don’t yet need a booster, an all-star panel of scientists from around the world said in a review that’s likely to fuel debate over whether to use them.

Governments would be better served to focus on immunizing the unvaccinated and to wait for more data on which boosters would be most effective and at what doses, the authors, who included two prominent U.S. Food and Drug Administration experts, argued in the medical journal The Lancet. They based their assessment on a wide range of real-world observational studies as well as data from clinical trials.

"None of the studies has provided credible evidence of substantially declining protection against severe disease,” the authors wrote. There could also be additional side-effect risks if boosters are introduced too soon or too broadly, they said.