Novavax's COVID vaccine nears the finish line

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Syringes filled with the Novavax COVID-19 vaccine were prepared for use at a vaccination center in Berlin, Germany, in February. Soon the vaccine could become available in the U.S. / Getty Images

A vaccine that may entice some people who have been hesitant to get vaccinated against COVID-19 appears to be highly effective, Food and Drug Administration scientists concluded in documents released Friday.

The vaccine, made by Novavax, Inc., of Gaithersburg, Md., was about 90% effective at preventing mild, moderate and severe COVID-19 when tested in a study involving about 30,000 volunteers ages 18 and older, according to the FDA.

The FDA scientists did, however, say a handful of cases of a rare form of heart inflammation that occurred among vaccine recipients is "concerning." The condition also been seen rarely in people who received other COVID-19 vaccines. In a statement, Novavax said "there is insufficient evidence to establish a causal relationship" between the vaccine and those cases.

The assessment was released in advance of a Tuesday meeting of advisers to the FDA about whether to recommend that the agency authorize the vaccine.

The vaccine, which requires two shots spaced 21 days apart, could appeal to some people who haven't been vaccinated because it uses a more traditional approach than the mRNA vaccines made by Moderna and Pfizer-BioNTech.

Those vaccines stimulate the immune system by injecting genetic code for a key protein from the SARS-CoV2 virus into the body. Although they are very safe and highly effective, some people have been reluctant to use them because the technology is new and because of misinformation about their safety.

"We all know that there are certain people in the population who are still concerned about a vaccine that is relatively new in the arena of vaccinology," says Dr. Anthony Fauci, the White House science adviser, told NPR in an interview. "And they may want a more classical vaccine that we have years and years of experience with."

The Novavax vaccine employs an approach that has been used for many other vaccines. It involves injecting a protein from the virus that is produced for the vaccine by insect cells. The protein then is combined with a substance known as an adjuvant to further stimulate the immune system.

"It's a very effective and proven way to make vaccines," Dr. Gregory Glenn, the president of research and training at Novavax, told NPR in an interview.

But others are skeptical whether those who are hesitant to get vaccinated would be swayed by the Novavax vaccine.

"I'm not sure I buy into that, unfortunately," says Saad Omer, who studies vaccines at Yale University. "It's not like there's a huge chunk of people just waiting for something other than an mRNA vaccine and will just get vaccinated. I don't think so."

A key question is how well the vaccine will work against the omicron variant, which wasn't circulating when the vaccine was tested. But the FDA scientists suspect it will be useful.

"Based on the efficacy estimate in the clinical trial of this vaccine, it is more likely than not that the vaccine will provide some meaningful level of protection against COVID-19 due to Omicron, in particular against more severe disease," FDA staff wrote.

The company is currently evaluating that question, as well as new version of the vaccine targeted specifically at omicron. Novavax is also testing how well its vaccine works as a booster after two shots of the Novavax vaccine as well as in people who have been vaccinated with the mRNA vaccines.

The federal government is trying to decide what kind of booster people should get in the fall to try to blunt the severity of a possible new wave of infections next winter. The panel of FDA advisers will meet late this month to consider which strains of the coronavirus should be targeted by updated vaccines.

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