Novavax Says Its COVID-19 Vaccine Is 89% Effective, Less So Against South African Variant

A coronavirus vaccine developed by Novavax is more than 89% effective in preventing COVID-19, the company announced Thursday, although it is not as useful in preventing infections of a fast-spreading variant of the virus that first emerged in South Africa.

Novavax, a Maryland biotech company that was supported by the federal government’s Operation Warp Speed, said results of its large-scale clinical trial were promising after studying 15,000 participants in the United Kingdom. The vaccine is also effective at preventing another, more-contagious variant of the virus that first began spreading in Britain. About half of the study participants were infected with that variant, known as B.1.1.7, which has become dominant in Britain and has struck fear as cases have popped up in other nations, including the U.S.

But Novavax said it noted a loss in efficacy of its vaccine in South Africa after studying a smaller sample of volunteers in the country. A mutated strain of COVID-19 has been widely circulating there, and Novavax found an overall protection of about 49%, raising concerns as to how effective vaccines will be should the virus continue to mutate as the pandemic drags on. (The vaccine’s efficacy rose to 60% among HIV-negative participants.)

The study also showed that almost a third of participants in South Africa tested positive for COVID-19 antibodies from the original coronavirus strain before they were infected by the new variant, suggesting some people had been infected twice and a natural immunity would not fully protect against it.

Moderna and Pfizer, which have both been given emergency authorization for their vaccines in the United States, have also said their products are not as effective against the South African strain. Even vaccines that have lower protection rates can still be useful, and the Food and Drug Administration initially said vaccines would need to have at least a 50% efficacy rate to be widely used as COVID-19 first began to spread.

Novavax’s president and chief executive, Stanley Erck, touted the company’s results on Thursday, despite the concerning figures.

“We have the first trial — we are the first to conduct an efficacy trial — in the face of a changing virus,” Erck told The New York Times this week. Erck added that the company would begin testing a new vaccine meant to combat the South African variant, pointing to the changing nature of the virus.

That news, however, is particularly concerning considering officials in South Carolina said they had discovered two cases of the South Africa variant that day, the first known cases in the U.S. Health officials have urged residents not to let up on social distancing measures, even as vaccination programs begin in earnest around the country, warning it will be many months before large segments of society are able to receive the immunizations.

The coronavirus has already killed more than 429,000 people in the U.S. and infected more than 25 million as health experts warn that, even with more vaccines arriving, tens or even hundreds of thousands of deaths are yet to come.