Novavax's Covid vaccine is 86 per cent effective against the UK strain of coronavirus, the variant spreading across the world and likely to become the dominant strain, results from the final analysis of the trial in Britain show.
There were no cases of severe illness or deaths among those who received the vaccine, the US company said – a sign that it could stop the worst effects of new variants that have cropped up.
It was 96 per cent effective in preventing cases caused by the original version of the coronavirus in a late-stage trial conducted in the UK, the company said, moving it a step closer to regulatory approval.
The vaccine was 86 per cent effective in protecting against the more contagious virus variant first detected and now prevalent in the UK, for a combined 90 per cent efficacy rate overall, based on data from infections of both versions of the coronavirus.
The UK trial, which enrolled more than 15,000 people aged 18 to 84, assessed efficacy of the vaccine during a period with high transmission of the UK variant now circulating widely.
The UK strain could be up to twice as deadly as previous variants.
Epidemiologists from the universities of Exeter and Bristol said after a study that the new highly infectious variant had a "significantly higher" mortality rate.
It is now "taking over" and causing 98 per cent of all cases in the UK, said the scientist leading the country's variant-tracking research.
Sharon Peacock, director of the Covid-19 Genomics UK consortium of scientists monitoring mutations in the coronavirus, said the UK variant – known as B117 – also appears to be gaining a grip in many of the 100 or so other countries it has spread to in the past few months.
"It's about 50 per cent more transmissible – hence its success in really taking over the country," Ms Peacock said.
Novavax shares jumped 22 per cent in after-hours trading to $229.
In a smaller trial conducted in South Africa – where volunteers were primarily exposed to a newer, more contagious variant widely circulating there and spreading around the world – the Novavax vaccine was 55 per cent effective, based on people without HIV, but it still fully prevented severe illness.
Novavax chief medical officer Filip Dubovsky said the performance in South Africa suggested there might still be a case for using it in areas where the South African variant was dominant.
Novavax is also developing new formulations of its vaccine to protect against emerging variants and plans to initiate clinical testing of these shots in the second quarter of this year.
Results from the final analysis of the UK trial were largely in line with interim data released in January.
The company expects to use the data to submit for regulatory authorisation in various countries. It is not clear when it will seek US approval or whether regulators will require it to complete an ongoing trial in the US.
Mr Dubovsky said Novavax was still planning to seek authorisation from UK regulators early in the second quarter of 2021.
The vaccine could be cleared for use in the US as soon as May if US regulators decide the UK data is enough to make a decision. It could take a couple months longer if they insist on first seeing data from the US trial, its chief executive said this month.
Novavax plans to produce its two-shot vaccine at eight manufacturing locations, including the Serum Institute of India.
If authorised, it would follow three Covid-19 vaccines previously approved for use in Britain, from Pfizer and partner BioNTech, Moderna Inc and the AstraZeneca shot developed with the University of Oxford. On Thursday, regulators recommended that the Johnson & Johnson vaccine be approved in Europe.
The Maryland-based company has received $1.6 billion from the US government in funding for the vaccine trial and to secure 100 million doses.
