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. The review comes as most countries with ample vaccine supplies debate whether to allocate doses for booster shots to prop up immunity and potentially help stop the spread of the more infectious delta variant.
The U.S. plans to roll out booster shots starting Sept. 20, though the plan still needs sign-off from the FDA and the Centers for Disease Control and Prevention.