Clinical trials of Novavax's Covid-19 vaccine have shown an efficacy of 89.3%, the US biotech company said in a statement on Thursday.
Good news quickly chased away by another: in a separate trial, it was found to be much less effective against the South African variant.
"NVX-CoV2373 has the potential to play an important role in solving this global public health crisis," said company CEO Stanley Erck, after the results of phase 3 trials involving more than 15,000 people in the Kingdom -United.
In the UK trial, Novavax observed 62 symptomatic Covid-19 cases, including 56 in the placebo group and six among the volunteers who received the vaccine.
A patient on placebo developed a severe Covid-19, compared to zero in the vaccinated group, according to the Statenews website.
But in another trial, conducted on 4,400 volunteers in South Africa, the vaccine was only 49% effective on the South African variant.