LONDON (Reuters) — Novavax Inc’s COVID-19 vaccine was 96% effective in preventing cases caused by the original version of the coronavirus in a late-stage trial conducted in the United Kingdom, the company said on Thursday, moving it a step closer to regulatory approval.

There were no cases of severe illness or deaths among those who got the vaccine.

The vaccine was also about 86% effective in protecting against the more contagious virus variant first discovered and now prevalent in the UK. It was about 90% effective overall, combining data from people infected with both versions of the coronavirus.

Novavax shares jumped 22% in after hours trading to $229. They were trading below $10 on Jan. 21, 2020, when the company announced it was developing a coronavirus vaccine.

In a smaller trial conducted in South Africa – where volunteers were primarily exposed to another newer, more contagious variant widely circulating there and spreading around the world – the Novavax vaccine was only around 55% effective but still fully prevented severe illness and death.

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 authorization in various countries. It is not clear when it will seek U.S. authorization or if regulators will require it to complete an ongoing trial in the United States.

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 virus variant now circulating widely.

The shot’s effectiveness in the South Africa trial declined to around 49% when the analysis included data from HIV-positive participants.

Novavax started a rolling submission of its vaccine data to the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) in mid-January, which should help speed the approval process.

The vaccine could be cleared for use in the United States as soon as May if U.S. 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 U.S. trial, its chief executive told Reuters earlier this month.

Novavax’s vaccine production plants should all be fully functional by April, executives said on a March investor call. The drugmaker expects to have tens of millions of doses stockpiled and ready to ship in the United States when it receives authorization, CEO Stanley Erck told Reuters.

Novavax plans to produce its two-shot vaccine at eight manufacturing locations, including the Serum Institute of India.

If authorized, 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 Oxford University.

Final results from the Novavax trial provide further hope as daily COVID-19 deaths spike in Britain, likely driven by the UK variant.