The Maryland-based biotech company Novavax reported Thursday that its experimental Covid-19 vaccine is more than 96 percent effective in preventing mild and severe illness.
The results are from the company's Phase 3 clinical trial, which was conducted in the U.K. Novavax's trials in the U.S. and South Africa continue, and the company cannot apply for emergency use authorization in the U.S. until the American trials are complete.
"We are very encouraged by the data," Stanley Erck, Novavax's president and CEO, said in a statement.
The U.K. trial included more than 15,000 adults. More than a quarter were 65 or older, an age group that is generally considered to be at higher risk for complications of Covid-19.
The two-dose vaccine was found to be more than 96 percent effective against earlier strains of the virus circulating in the U.K., putting it on par with vaccines already in use from Moderna and Pfizer-BioNTech.
Effectiveness was slightly lower — around 86 percent — against the more contagious B.1.1.7 variant, which was first identified in the U.K. The variant has already been detected in nearly half of U.S. states, and the Centers for Disease Control and Prevention has predicted that it will be the predominant variant by the end of the month.
The Novavax vaccine was also 100 percent effective against the most severe forms Covid-19, regardless of the variant — much like the other vaccines in use in the U.S.
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The Biden administration has promised enough vaccine for all eligible Americans by the end of May. The goal is expected to be met with vaccines that are already available, from Moderna, Pfizer-BioNTech and Johnson & Johnson.
Other vaccines that ultimately prove to be successful will be critical to the health and safety of Americans in a post-Covid-19 environment in which viruses can travel from country to country as fast as airplanes.
"The United States isn't safe until the vast majority of the rest of the world is vaccinated," said John Grabenstein, a former executive director of medical affairs for vaccines at Merck and a former Defense Department immunologist.
Novavax also analyzed data from its Phase 2b clinical trial in South Africa, where another SARS-CoV-2 variant has been circulating. The variant, called B.1.351, concerns scientists because it appears to lower vaccine effectiveness. Novavax found its vaccine to be around 50 percent effective against the variant.
The Novavax vaccine differs slightly from the other vaccines in use. The Pfizer, Moderna and Johnson & Johnson vaccines all provide instructions for the body to build the coronavirus's spike protein, which the immune system learns to recognize and fight. The Novavax shot skips the instructions and delivers the spike protein directly to the body.
If it is ultimately approved for use, the Novavax shot could serve as "another shield we can use to protect against a nasty virus," Grabenstein said.
More than 98 million doses of vaccines have been administered, according to the CDC, with nearly 34 million people having been fully vaccinated.