A trial in South Africa of an experimental coronavirus vaccine made by US vaccine maker Novavax shows the vaccine is about 50% effective against a variant that’s now the dominant strain in that country. It also shows that the vaccine offers better protection from the new variant than antibodies from people previously infected with coronavirus.
The researchers say their findings, which had been shared previously in a statement from Novavax, show the importance of quick and widespread vaccination to prevent the worse spread of variants.
The team led by Tulio de Oliveira of the University of KwaZulu-Natal was conducting a mid-size, Phase 2 safety and efficacy trial of the vaccine in about 4,000 volunteers in South Africa when the B.1.351 variant was by far the most common circulating type of virus.
“The NVX-CoV2373 vaccine was efficacious in preventing Covid-19, which was predominantly mild to moderate and due to the B.1.351 variant, while evidence of prior infection with the presumptive original SARS-CoV-2 did not confer protection against probable B.1.351 disease,” they wrote in a preprint report. That report hasn’t been peer reviewed but it has been posted online.
“Among 94% of participants without HIV, vaccine efficacy was 60.1%. The study was not powered to detect efficacy in the small population of people living with HIV,” they wrote. Overall efficacy in preventing symptomatic infection was about 50%.
About 30% of the volunteers had evidence of a previous coronavirus infection when they enrolled. When these volunteers got placebo shots, they were just as likely to catch coronavirus as those who got real vaccine, the researchers reported. That’s evidence that previous infection with a different variant provides little protection against B.1.351.
“This finding has significant public health implications for pandemic modeling, control strategies, and vaccine development and deployment efforts,” the team wrote in the preprint posted Wednesday.
But the vaccine did provide protection against the new variant – although much lower than the 89% efficacy shown in a more advanced, Phase 3 trial in the UK.
Novavax plans to apply for US Food and Drug Administration emergency use authorization of its Covid-19 vaccine sometime in the second quarter of this year. It’s testing 30,000 volunteers in the US and Mexico for that application.
The company has said it is already working on booster shots to help its vaccine protect against newly emerging variants of the coronavirus.