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 shares surged more than 17% before the bell on Monday, following the long-delayed approval of its COVID-19 vaccine from the U.S. health regulator, albeit with new conditions.

The U.S. Food and Drug Administration approved Novavax's COVIDd-19 vaccine with age restrictions after a six-week delay.