Drugmaker Pfizer has announced that the early results of the COVID-19 vaccine it has developed with Germany's BioNTech SE shows that it is 90% effective at preventing people contracting the virus.
The announcement Monday has been described as a "significant step" in the fight against the virus, which follows testing on 43,500 people in six countries, of which only 94 people contracted the virus. Otherwise, no safety concerns were noted.
The vaccine requires two doses taken three weeks apart, which the immunity presents seven days after the second dose.
The companies are intending to apply for emergency approval in the U.S. via the Food and Drug Administration by the third weekend of November.
There remain some uncertainties over the vaccine, not least that it's not yet known how long the immunity it provides lasts, it has not been peer reviewed, it's not known if the vaccine prevents severe cases, or whether it can stop people carrying the virus asymptomatically.
What's more, there could be logistical challenges presented by the fact that the vaccine needs to be stored at temperatures below -80C.
Pfizer says it can produce 50 million doses – enough for 25 million people – by the end of 2020, and a further 1.3 billion in 2021.
The news was welcomed by President Donald Trump, who tweeted: "STOCK MARKET UP BIG, VACCINE COMING SOON. REPORT 90% EFFECTIVE. SUCH GREAT NEWS!"
Meanwhile, President-Elect Joe Biden thanked the "brilliant men and women who helped produce this breakthrough and to give us cause for such hope."
But he also cautioned that it's likely to take a significant amount of time to get any approved vaccine rolled out nationwide, and as such Americans should continue to take precautions – such as wearing face masks – to prevent the virus' spread at a time when cases are surging particularly in the Midwest.