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Novavax says its Covid-19 vaccine is 89.3 percent effective

The vaccine also appears to protect against the U.K. and South African variants, although efficacy was lower for the South African strain.
A vial with a potential Covid-19 vaccine at Novavax labs in Rockville, Md., on March 20.Andrew Caballero-Reynolds / AFP - Getty Images file

An experimental coronavirus vaccine developed by the biotech company Novavax is 89.3 percent effective at preventing Covid-19, the company announced Thursday.

Results from Novavax's Phase 3 trial in the United Kingdom demonstrated the vaccine candidate's efficacy and showed that it protected against the U.K. variant of the virus. Results from another trial, in South Africa, showed that it was also effective against the variant that emerged there, although efficacy was lower.

Stanley Erck, president and CEO of Novavax, based in Gaithersburg, Maryland, said the trial results show that the vaccine "has the potential to play an important role in solving this global public health crisis."

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Novavax, which received funding last year as part of the Trump administration's Operation Warp Speed, is conducting vaccine trials in the United States, the U.K., Mexico and South Africa.

An interim analysis of the company's trial in the U.K., which included more than 15,000 participants ages 18 to 84, found that the vaccine was 95.6 percent effective against the virus and 85.6 percent effective against the more contagious U.K. variant.

The findings were based on 62 infections among trial participants, who received either a two-dose vaccination or a placebo. Six of the observed infections occurred in the group that got the vaccine.

In the Phase 2 South Africa trial, however, efficacy was 49.4 percent. The study was carried out on a much smaller group of 4,400 people, many of whom were HIV-positive. In trial participants who were HIV-negative, the vaccine was 60 percent effective at preventing symptomatic Covid-19, Novavax said.

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Novavax's analysis was based on 44 infections among participants in the South African trial, of which 15 cases were reported in the group that got the vaccine. Ninety percent of the Covid-19 cases analyzed in the trial were caused by the South African variant, the company reported.

Moderna announced this week that its vaccine appears to be less effective against the South African variant, although it said protective antibodies remained above protective levels. A Pfizer study, which has not been peer-reviewed, found that the Pfizer-BioNTech vaccine is only slightly less effective against the South African strain.

Unlike the vaccines developed by Pfizer-BioNTech and Moderna, which use snippets of genetic code known as messenger RNA to trigger the immune system to produce protective antibodies, Novavax's vaccine relies on synthesized coronavirus proteins to jump-start the body's immune system.