Novavax COVID-19 vaccine 89% effective in late-stage trials; less efficacy seen against South African variant

The Maryland-based biotech firm Novavax on Thursday announced the results of its late-stage clinical trial in Britain, finding that its two-dose coronavirus jab was around 89% effective in preventing COVID-19 illness. 

The company’s study on its vaccine involves some 15,000 participants between the ages of 18 and 84 and is ongoing. However, in an interim analysis, the company said that only 62 participants contracted COVID-19 — only six of whom received the jab and the rest who received a placebo. 

Additionally, the company noted its vaccine appears to be effective against a virus variant that was first discovered in the United Kingdom late last fall. Novavax in a news release regarding the results said its shot appeared to be nearly 86% effective against the U.K. strain, known as B.1.1.7. 

“The interim analysis included a preliminary review of the safety database, which showed that severe, serious, and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups,” the company added in the news release.

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Clive Dix, the chair of the U.K. Vaccine Taskforce, called the results “spectacular.”

“We are very pleased to have helped Novavax with the development of this vaccine,” he said. “The efficacy shown against the emerging variants is also extremely encouraging. This is an incredible achievement that will ensure we can protect individuals in the UK and the rest of the world from this virus.”

That said, the vaccine appeared to be less effective against a concerning variant of the coronavirus first identified in South Africa that carries different mutations.

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Results from a smaller Novavax study in that country suggests 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 appears 60% effective. Including volunteers with HIV, overall the protection was 49%, the company said. While 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 mutant.

Novavax said it needs some additional data before it can seek British authorization for the vaccine’s use, sometime in the next month or so. A larger study in the U.S. and Mexico has enrolled slightly over half of the needed 30,000 volunteers. Novavax said it’s not clear if the Food and Drug Administration will need data from that study, too, before deciding whether to allow U.S. use.

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Meanwhile, it is starting to develop a version of the vaccine that could more specifically target the mutations found in South Africa, in case health authorities eventually decide that updated dosing is needed.

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. 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.

The Associated Press contributed to this report.