A fourth Covid vaccine is cleared for use in the United States.

The Centers for Disease Control and Prevention on Tuesday recommended that a newly licensed vaccine from Novavax be used as an option for adults seeking a primary vaccination against the coronavirus.

Dr. Rochelle Walensky, director of the CDC, endorsed the recommendation of a panel of vaccine experts who had unanimously approved the vaccine on Tuesday afternoon. The decision removes the final regulatory hurdle for the fourth Covid-19 vaccine authorized in the United States.

The Novavax vaccine is expected to play a limited role in the country’s vaccination campaign, at least initially. Last week, the Food and Drug Administration authorized it as a primary vaccination for adults, but has not yet considered it for a booster shot.

Novavax, a pharmaceutical company in Maryland, received significant federal funding to develop its vaccine, but fell far behind in the vaccine race. Still, he hopes the vaccine will appeal to Americans who have so far refused to get vaccinated.

Somewhere between 26 million and 37 million adults in the United States have yet to receive a coronavirus vaccine, according to survey data presented at the meeting by CDC’s Dr. Katherine Fleming-Dutra

But in countries where it has been available for months, Novavax’s vaccine has yet to have a significant effect on vaccination rates. Novavax said in its presentation to the panel on Tuesday that just over a million doses of its vaccine had been administered worldwide through the end of June, only a tiny fraction of the reach of competing injections.

The Biden Administration said last week that it would purchase 3.2 million doses of the two-shot vaccine from Novavax, enough to fully vaccinate 1.6 million people in the United States. The vaccine is not yet available in pharmacies and other clinics that administer injections. Novavax said in a press release after the vote that the FDA had approved the first doses destined for the United States and that the company planned to ship its vaccine to a distribution center “in the coming days”.

With two doses spaced three weeks apart, the vaccine has been shown to be highly protective against infection and serious illness from the coronavirus in clinical trials. But these were conducted before the emergence of the Omicron variant, which sharply reduced the effectiveness of other licensed vaccines in preventing infections.

Novavax’s vaccine works differently from the three Covid vaccines previously licensed in the United States. This provokes an immune response with nanoparticles consisting of proteins from the surface of the coronavirus that causes Covid-19. Similar protein-based vaccines have been used around the world for decades.

CDC’s Dr. Evelyn Twentyman presented survey results suggesting that relatively few unvaccinated Americans would choose Novavax. Only 16% of unvaccinated respondents said they would ‘probably’ or ‘definitely’ receive a protein-based Covid vaccine, and 50% of unvaccinated respondents said they ‘probably’ or ‘definitely’ would not. not.

At Tuesday’s meeting, CDC officials reviewed clinical trial data that linked the vaccine to a high but low risk of developing forms of heart inflammation called myocarditis and pericarditis.

Dr. Filip Dubovsky, Novavax’s chief medical officer, told the meeting that the company was monitoring cases of heart inflammation in countries where the vaccine was already licensed. By reviewing just over a million doses, the company identified 17 definite or probable cases of myocarditis and pericarditis, he said.