Drugmakers and research centres around the world are working on COVID-19 vaccines, with large global trials of several candidates involving tens of thousands of participants.
The following is what we know about the race to deliver vaccines to help end the coronavirus pandemic that has claimed more than 1.34 million lives worldwide:
WHO IS FURTHEST ALONG?
US drugmaker Pfizer Inc and German partner BioNTech SE released final trial data in November that showed their shot was 95 per cent effective at stopping COVID-19, the highest efficacy rate so far.
Also in November, US pharmaceutical company, Moderna Inc, released interim data showing its vaccine worked in a late-stage clinical trial with a 94.5 per cent efficacy rate.
Interim late-stage trial results for Russia's Sputnik V vaccine published on November 11 showed it to be 92 per cent effective.
AstraZeneca said on Monday its vaccine for the novel coronavirus, developed by Oxford University, could be around 90 per cent effective with the right dosage pattern, without any serious side effects.
WHAT HAPPENS IN THESE TRIALS?
The companies are testing their vaccines against a placebo - typically saline solution - in healthy volunteers to see if the rate of COVID-19 infection among those who had the vaccine is significantly lower than in those who received the dummy shot.
The trials rely on subjects becoming naturally infected with the coronavirus, so how long it takes to generate results largely depends on how pervasive the virus is where trials are being conducted. Each drugmaker has targeted a specific number of infections to trigger a first analysis of their data.
Early in the trials, infection rates were low. With a surge in infections around the globe in October and November, trial participants became infected more quickly.
HOW WELL ARE THE VACCINES SUPPOSED TO WORK
The World Health Organisation ideally wants to see at least 70 per cent efficacy in trials. The US Food and Drug Administration wants at least 50 per cent - which means there must be at least twice as many infections among volunteers who received a placebo as among those in the vaccine group. The European Medicines Agency has said it may accept a lower efficacy level.
WHEN WILL REGULATORS RULE ON SAFETY AND EFFICACY?
Pfizer/BioNTech plan to submit an EUA application in the United States within days. Moderna aims to file an application in the coming weeks once it has the two months of safety data on half the trial participants, as required by the US Food and Drug Administration. That should happen in the second half of November.
AstraZeneca said on Monday it will immediately prepare regulatory submission of its data to authorities around the world that have a framework in place for conditional or early approval.
COULD THESE BE THE FIRST WIDELY AVAILABLE CORONAVIRUS VACCINES?
Yes, although China launched an emergency use program in July aimed at essential workers and others at high risk of infection that has vaccinated hundreds of thousands of people.
At least four Chinese vaccines are being developed including those from China National Biotec Group (CNBG), CanSino Biologics and Sinovac Biotech.
Russia has also given the Sputnik V vaccine developed by the Gamaleya Institute to 10,000 members of the general population considered at high risk of contracting the virus.
Australian Associated Press