Pfizer has said that final results from the late-stage trial of its Covid-19 vaccine show it is 95% effective, adding it had the required two months of safety data and would apply for emergency US authorisation within days.
The drugmaker said efficacy of the vaccine developed with German partner BioNTech was consistent across age and ethnicity demographics.
It also said there were no major side effects, a sign that the immunisation could be employed broadly around the world.
Efficacy in adults over 65 years, who are at particular risk from the virus, was over 94%.
The final analysis comes just one week after initial results from the trial showed the vaccine was more than 90% effective.
Moderna on Monday released preliminary data for its vaccine, showing similar effectiveness.
The better-than-expected data from the two vaccines, both developed with new technology known as messenger RNA (mRNA), have raised hopes for an end to a resurgent pandemic that has killed more than 1.3 million people globally and wreaked havoc upon economies and daily life.
However, while some groups such as healthcare workers will be prioritised in the US for vaccinations this year, it will be months before large-scale rollouts begin.
Pfizer said there had been 170 cases of the disease in its trial of more 43,000 volunteers, of which 162 were observed in the placebo arm and eight were in the vaccine group.
Ten people developed severe Covid-19, one of whom received the vaccine.
It also said the vaccine was well-tolerated and that side effects were mostly mild to moderate and cleared up quickly.
The only severe adverse event that affected more than 2% of those vaccinated was fatigue, which affected 3.7% of recipients after the second dose. Older adults tended to report fewer and milder solicited adverse events following vaccination.
The results come as the virus is running rampant in the United States, Europe and elsewhere, placing an enormous strain on healthcare systems with record numbers of new cases and hospitalisations.
"With hundreds of thousands of people around the globe infected every day, we urgently need to get a safe and effective vaccine to the world," Pfizer CEO Albert Bourla said in a statement.
Pfizer and BioNTech also said they plan to submit the data to other regulatory agencies around the world as well as the United States. They also plan to submit data from the study to a peer-reviewed scientific journal.
Pfizer reiterated it expects to make as many as 50 million vaccine doses this year, enough to protect 25 million people, and then produce up to 1.3bn doses in 2021.
Of the dozens of drugmakers and research groups racing to develop vaccines against Covid-19, the next data release will likely be from AstraZeneca with the University of Oxford this month or next month.
Johnson & Johnson says it is on track to deliver data this year.