Shares in Novavax have soared after the Maryland-based biotech firm announced stellar results from trials of its COVID-19 vaccine.

In a large-scale Phase III trial conducted in the U.K., the jab proved to be 96.4% effective against mild, moderate, and severe disease caused by the original coronavirus strain. In a more preliminary Phase IIb trial Novavax is running in South Africa—where newer, more transmissible variants are widespread—results suggested 55.4% efficacy among participants who are HIV-negative, and 48.6% efficacy when HIV-positive trial participants were taken into account.

In both trials, the vaccine showed 100% protection against hospitalization or death caused by COVID-19.

“Today marks one year since the WHO officially declared the COVID-19 pandemic, and with this data in hand, we are even more motivated to advance our vaccine as a potential weapon in the fight to end the suffering caused by COVID-19,” Novavax CEO Stanley Erck said in a statement.

Investors are clearly also feeling motivated, because Novavax’s share price rose by more than 20% on the news.

The company may need to complete its U.S. late-stage trial—which was repeatedly delayed due to production issues—before it can apply for emergency use authorization there.

Erck said earlier this month that he hoped to receive the U.S. green light in May, with a rollout beginning in the middle of the year. Novavax already has a $1.6 billion deal with the U.S. government to supply 110 million doses.

The U.K. has ordered 60 million doses of the vaccine, and Health Secretary Matt Hancock signaled high hopes following Novavax’s announcement. If approved by the British drug regulator—Novavax chief medical officer Filip Dubovsky told the Telegraph an application would be filed in early Q2—those doses will be manufactured on Teesside, in North East England.

In the EU, the European Commission has had exploratory talks with Novavax about supplying up to 200 million doses to the bloc. The European Medicines Agency (EMA) is already reviewing the vaccine, along with candidates from Germany’s CureVac and Russia’s Sputnik V.

Like AstraZeneca’s vaccine, Novavax’s jab has the advantage that it can be stored and transported at normal refrigeration temperatures. This has big logistical implications, given that already approved vaccines from Pfizer and Moderna require much lower temperatures—though the U.S. Food and Drug Administration recently said Pfizer’s vaccine can be kept at standard freezer temperatures for a couple of weeks, rather than the ultracold temperatures that were originally advised.