Those of you who, for various reasons, have yet to get a Covid-19 booster shot now have an option that’s not a messenger RNA vaccine. The FDA on Wednesday authorized Novavax’s vaccine as a first booster shot.

The regulatory decision covers those 18 and older who don’t have access to an authorized bivalent mRNA booster as well as those can’t take an mRNA vaccine for medical reasons. The authorization also covers adults who choose the Gaithersburg, Maryland-based company’s vaccine because they would otherwise not receive a booster shot at all.

The Centers for Disease Control and Prevention issued a recommendation for the Novavax booster shots Wednesday afternoon, the last regulatory requirement before pharmacies and other vaccine providers can start administering the shots.

The Novavax vaccine, NVX-CoV2373, was granted a long-awaited FDA authorization in adults in July, making it a latecomer to the market following authorizations and then approvals for the mRNA shots from Moderna and partners Pfizer and BioNTech, and an authorization for Johnson & Johnson’s shot. In August, the FDA authorized the Novavax vaccine for adolescents 12 to 17.

Novavax’s protein-based vaccine, given as a two-shot primary series, is engineered from the original strain of SARS-CoV-2. Using nanoparticle technology, Novavax generates antigen derived from the spike protein of the novel coronavirus. This vaccine contains an adjuvant, an ingredient that boosts the immune response.

Like the mRNA booster vaccines, Novavax’s booster is a single shot that may be given six months or later following primary vaccination with any of the authorized or approved Covid-19 vaccines. But the authorization covers its use only as the first booster. For the omicron variant, the only “updated” boosters that the FDA has authorized so far are mRNA vaccines from Moderna and Pfizer/BioNTech.

Novavax’s omicron efforts are still in clinical testing. One vaccine is a monovalent shot based on the omicron strain. Another one is a bivalent vaccine that addresses both the original strain and omicron. While Novavax continues to develop these updated vaccines, it will have plenty of opportunity to try and reach the unboosted. Nearly 68% of the U.S. population has completed the primary series of Covid-19 vaccination, but less than half of them have received their first booster, according to data compiled by the Centers for Disease Control and Prevention.

“Offering another vaccine choice may help increase Covid-19 booster vaccination rates for these adults,” Novavax President and CEO Stanley Erck said in a prepared statement.

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