Novavax's (NVAX) COVID-19 vaccine has been approved for use by the US Food and Drug Administration but limited to only those over 65 years old and to those over 12 years old with underlying medical conditions, news outlets reported Saturday, citing company officials.

Reuters cited Novavax's Chief Corporate Affairs and Advocacy Officer Silvia Taylor as saying the approval for the drug, sold under the name Nuvaxovid, came late Friday night.

Novavax did not immediately reply to MT Newswires' request for comment.

Novavax Chief Executive John Jacobs described the approval as a "significant milestone" in a statement cited by Reuters.

Shares of the US biotech firm were up more than 16% in recent premarket activity Monday.

Price: 7.86, Change: +1.13, Percent Change: +16.79