The biotech company Novavax says its COVID-19 vaccine is 89% effective at preventing the illness, according to an interim analysis of a large study conducted in the U.K.
The results come from a clinical trial involving more than 15,000 volunteers, of whom more than a quarter were older than 65.
The company says 62 cases of COVID-19 were seen in the study. Fifty-six occurred in the group that got placebo; six were seen in people who received the vaccine.
The Novavax vaccine is what's called a protein subunit vaccine, a different kind of vaccine technology that is used in the shots made by Pfizer and Moderna that are being rolled out in this country. The Novavax vaccine is given in two doses spaced 21 days apart.
Novavax says in a news release that its vaccine is slightly less effective against the new variant of the coronavirus that's been circulating in the U.K. — about 86%. Against the original COVID-19 strain, the vaccine is about 96% effective, the company says.
In a separate, smaller study in South Africa, the vaccine was still somewhat effective at preventing COVID disease — 49% overall — a level far lower than in the larger U.K. study. But there is a wide range of uncertainty around exactly how much lower the effectiveness is.
A preliminary analysts suggested the variant strain first identified in South Africa appeared to be responsible for the majority of the COVID cases seen in the study.
After vaccination or previous infection, the immune system is able to make antibodies that recognize the coronavirus and then neutralize or destroy it. As the virus mutates, however, it can change how it looks to these antibodies and make it harder for them to lock on.
A combination of mutations in the variant first seen in South Africa changed the surface of the virus where antibodies seek to bind.
The Novavax study in South Africa found that a previous infection with the original form of the virus that causes COVID-19 may not completely protect people against becoming infected with the mutated version later on.