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.

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

The U.S. Food and Drug Administration on Friday approved Novavax's COVID-19 vaccine, but placed additional conditions on individuals who would be able to receive the vaccine. According to the approval letter,