Novavax vaccine 89 per cent effective in British trial Julie Steenhuysen Save Share Chicago | Novavax said on Thursday (Friday AEST) that its coronavirus vaccine was 89.3 per cent effective in preventing COVID-19 in a trial conducted in Britain, and was nearly as effective in protecting against the more highly contagious variant discovered there, according to a preliminary analysis. A mid-stage trial of the vaccine in South Africa, where a troubling new variant of the virus is common, showed 60 per cent effectiveness among people who did not have HIV. Novavax said the trial, which enrolled 15,000 people aged 18 to 84, was expected to be used to apply for regulatory review in Britain.Â