Novavax vaccine seems effective against COVID-19 in early U.K. study

People are seated on hospital beds; one reads a book.
Clinical trial participants are monitored during Novavax COVID-19 vaccine testing in Melbourne, Australia.
(Patrick Rocca / Associated Press)

Novavax Inc. said Thursday that its COVID-19 vaccine appeared to be 89% effective based on early findings from a British study and that it also seemed to work — though not quite as well — against new strains of the virus circulating in the U.K. and South Africa.

The announcement comes amid worry about whether a variety of vaccines being rolled out around the world will be effective against worrisome new variants, and at a time when new shots are needed to boost scarce supplies.

The study of 15,000 people in Britain is still underway. But an interim analysis found 62 participants so far had been diagnosed with COVID-19. Six were from the group that received the vaccine, and the rest had received dummy shots.


The infections occurred at a time when Britain was experiencing a jump in coronavirus cases that involve a more contagious variant. A preliminary analysis found that more than half of the trial participants who had become infected had the new strain. The numbers are very small, but Novavax said they suggested the vaccine was nearly 96% effective against the older coronavirus and nearly 86% effective against the new variant.

Scientists have been even more worried about a strain first discovered in South Africa that carries different mutations — and results from a smaller Novavax study suggest the vaccine does work but not nearly as well as it does against the variant from Britain.

The South African study included some volunteers with HIV. Among the HIV-negative volunteers, the vaccine appeared 60% effective. Including the volunteers with compromised immune systems, overall the protection was 49%, the company said. Although genetic testing still is underway, so far about 90% of the COVID-19 illnesses found in the South African study appear due to the new strain.

The preliminary findings may help Novavax win authorization for its vaccine in Britain, but the U.S. government is funding a far larger study that’s still recruiting volunteers.

Vaccines against COVID-19 train the body to recognize the new coronavirus, mostly the spike protein that coats it. But the Novavax candidate is made differently than the first shots being used. For what’s called a recombinant protein vaccine, the Maryland company uses genetic engineering to grow harmless copies of the coronavirus spike protein in insect cells. Scientists extract and purify the protein and then mix in an immune-boosting chemical.