After a six-week delay, the US Food and Drug Administration has approved Novavax’s Covid-19 vaccine, according to a letter from the agency, but only for people 65 and older and those 12 and up who have at least one underlying condition that puts them at higher risk of severe illness.

Novavax later announced the FDA instead was asking it to run an additional trial after approval, which is highly unusual. FDA did order several additional trials to be completed i

The agency narrowed who can get the shot and added new study requirements that could cost the company tens of millions.