The drug company Pfizer said Monday that early analysis showed its vaccine candidate for COVID-19 is more than 90% effective at preventing infection.
The news from U.S. pharmaceutical giant Pfizer and its German partner, BioNTech SE, has been welcomed as a major step in the fight against a virus that has plagued the global economy, upended daily life for billions and killed 1.26 million people — nearly 240,000 in the U.S. alone.
President-elect Joe Biden said he welcomed the news, which he said he learned Sunday night, but warned it was "important to understand that the end of the battle against COVID-19 is still months away."
Even if "some Americans are vaccinated later this year, it will be many more months before there is widespread vaccination in this country," Biden said in a statement. "Today's news does not change this urgent reality. Americans will have to rely on masking, distancing, contact tracing, hand washing, and other measures to keep themselves safe well into next year."
Though the findings are preliminary, the Pfizer-led study indicates a far higher success rate than many experts had expected. People who received two doses as part of the trial saw 90% fewer symptomatic cases of COVID-19 than participants who were given a placebo.
Pfizer has not released the full results of the study.
"Today is a great day for science and humanity," Albert Bourla, Pfizer's chairman and chief executive, said in a statement. "We are reaching this critical milestone in our vaccine development program at a time when the world needs it most with infection rates setting new records, hospitals nearing over-capacity and economies struggling to reopen."
John Bell, an Oxford University professor and vaccines adviser to the U.K. government, welcomed the news and went as far as to say life could begin to return to normal by spring.
"Yes, I'm probably the first guy to say that but I will say that with some confidence," he said when asked by the BBC whether that timeline was now realistic.
In spite of the optimism, the news does not mean a vaccine will be immediately available.
Though there have been no serious safety concerns yet, Pfizer also said, the company added that it would not apply to the U.S. Food and Drug Administration for emergency use authorization until it had two months worth of safety data, which will likely not come until the third week of November.
It is also unclear how long any protection would last, although BioNTech's chief executive, Ugur Sahin, told Reuters, "We should be more optimistic that the immunization effect can last for at least a year." He said it was basing this on earlier findings and research on recovered patients.
Even if approved, rolling out the vaccine worldwide will be an unparalleled logistical challenge. Like many others, this vaccine must be kept at super-cold temperatures, meaning distribution to remote parts of the world will be difficult.
Pfizer said that based on current projections it expects to produce globally up to 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021.
Regardless of the unknowns, international markets welcomed the news, with stock futures on Wall Street surging after the announcement.
A version of this story originally appeared on NBCNews.com.