Novavax vaccine has 96% efficacy against original COVID-19 strain, 55.4% against South Africa variant

Vaccine developer Novavax announced on Thursday that its vaccine offers high levels of protection against the original coronavirus strain that causes COVID-19, but the vaccine’s efficacy is diminished by some coronavirus variants, including one that originated in South Africa.

Novavax announced on Twitter that its vaccine has 96% efficacy against the original strain of the coronavirus, according to a recent U.K. trial. 

But the company said its vaccine is only 55.4% effective against the B.1.351 strain, first detected in South Africa in December. The South Africa strain has been reported in several states in the U.S.

The announcement comes amid worry about whether the vaccines being rolled out around the world will be strong enough to protect against worrisome new variants – especially as the world desperately needs new types of shots to boost scarce supplies.

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Last month, Moderna announced that it has shipped doses of its COVID-19 vaccine booster designed specifically to offer better protection against the South Africa coronavirus variant to the National Institutes of Health (NIH) for a Phase 1 clinical trial.

A separate laboratory study published in February by  Pfizer Inc/BioNTech, the first company to get emergency authorization for its COVID-19 vaccine, suggested that its current vaccine may generate a significantly less robust antibody response against the South Africa variant of the virus. 

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According to the in vitro study published in the New England Journal of Medicine (NEJM), lab results "indicated a reduction in neutralization," of the virus.

"This finding is consistent with recent reports of the neutralization of variant SARS-CoV-2," Pfizer wrote in a news release published last month.

Researchers analyzed blood from people who had taken the Pfizer coronavirus vaccine and identified a two-thirds reduction in the level of neutralizing COVID-19 antibodies to the South Africa variant.

This was compared with the most common variant of the virus prevalent in the U.S.

Researchers from Pfizer said it remains unclear what effect the diminished immune response to the South Africa variant has on the vaccine’s overall protection from the virus.

As the U.S. rushes to vaccinate as many Americans as possible amid the rising concern of other COVID-19 variants, Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, said the next two months are critical for the nation to prevent a possible next wave of COVID-19.

"There is so much that's critical riding on the next two months," Walensky said, speaking at a National League of Cities virtual conference on Monday. "How quickly we will vaccinate versus whether we will have another surge really relies on what happens in March and April."

President Joe Biden on Wednesday directed his administration to order another 100 million doses of the Johnson & Johnson coronavirus vaccine, growing a likely U.S. surplus of doses later this year while much of the rest of the world struggles with deep shortages.

Even before Wednesday's order, the U.S. was to have enough approved vaccine delivered by mid-May to cover every adult and enough for 400 million people total by the end of July. Enough doses to cover 200 million more people are on order should vaccines from AstraZeneca and Novavax receive approval from the Food and Drug Administration. The new J&J doses, which would cover another 100 million people, are expected to be delivered in the latter half of the year.

RELATED: CDC director says next 2 months critical in stopping another COVID-19 surge

A more contagious and possibly more deadly variant that was first identified in Britain has been found in at least 42 states. Other variants first detected in South Africa and Brazil have been reported across the U.S. in low numbers. The South Africa mutation is especially worrisome because of evidence it may diminish the effectiveness of the vaccines.

With some U.S. states, like Texas, dropping mandates to stop the spread of COVID-19 as more and more residents get vaccinated, medical experts are warning that these reopenings are premature and could lead to another deadly surge.

Scientists widely agree that the U.S. simply doesn’t have enough of a handle on the variants to roll back public health measures and is at risk of fumbling yet another phase of the pandemic after letting the virus rage through the country over the last year, killing over 530,000 people.

The Associated Press contributed to this story.