What happened

Shares of Novavax (NVAX 2.06%) were jumping 5% higher as of 10:33 a.m. ET on Wednesday after rising as much as 11.2% earlier in the day. The gain came after the U.S. Centers for Disease Control and Prevention (CDC) cleared the way on Tuesday for Novavax's COVID-19 vaccine (NVX-CoV2373) to be used as a two-dose primary series in individuals ages 18 and older.

So what

The CDC's decision came after its Advisory Committee on Immunization Practices (ACIP) unanimously voted to recommend Novavax's vaccine. The U.S. Food and Drug Administration (FDA) granted Emergency Use Authorization (EUA) to NVX-CoV2373 last week. 

Even with today's gain, Novavax's share price remains below the levels from the days leading up to the FDA's authorization. The vaccine stock plunged last week despite the positive FDA decision, primarily on worries about a report about potential side effects for NVX-CoV2373 and slow uptake in the European Union.

The CDC's action is an important milestone for Novavax. However, the relatively muted reaction from investors reflects uncertainty about how many unvaccinated Americans will choose to receive NVX-CoV2373.

Now what

Novavax stated in a press release that it expects to begin shipping doses of NVX-CoV2373 to distribution centers designated by the U.S. government in the next few days. Within a matter of weeks, investors should have a better sense of how Americans respond to the availability of a new COVID-19 vaccine.

Arguably the most important next step for Novavax, though, is to secure EUA for its booster targeting the coronavirus omicron variant. The company has said it hopes to have this booster ready in the fourth quarter of 2022.