NEW YORK/LONDON (REUTERS) - Drugmakers and research centres around the world are working on Covid-19 vaccines, with large global trials of several of the candidates involving tens of thousands of participants well underway.
The following is what we know about the race to deliver vaccines to help end the coronavirus pandemic that has claimed over 1.26 million lives worldwide:
Q: Who is furthest along?
A: Moderna is the second US pharmaceutical company to release interim data showing that its vaccine worked in a large, late-stage clinical trial. The biotech firm said its vaccine was 94.5 per cent effective.
One week ago, US drugmaker Pfizer and German partner BioNTech released interim data and said their shot was more than 90 per cent effective at stopping Covid-19.
Interim late-stage trial results for Russia's Sputnik V vaccine published on Nov 11 showed the shot is 92 per cent effective.
The next data release will likely be from AstraZeneca with the University of Oxford in November or December.
Johnson & Johnson says it is on track to deliver data this year.
Q: What happens in these trials?
A: 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 got the vaccine is significantly lower than in those who received the dummy shot.
Q: What were pharma companies waiting for to release data?
A: 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.
Moderna conducted its interim analysis after 95 participants developed Covid-19. Pfizer's was done after 94 developed Covid-19 while Russia's examination was conducted after 20 developed the disease.
AstraZeneca said two weeks ago that a slowdown in infections during the summer is delaying data analysis for its UK trial.
Q: How well are the vaccines supposed to work?
A: 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.
Q: When will regulators rule on safety and efficacy?
A: Moderna and Pfizer/BioNTech plan to submit applications seeking US emergency use authorisation (EUA) in the coming weeks after they have enough safety data, which they have said would be in the second half of November.
That means the earliest the US Food and Drug Administration could make a decision is December. The FDA has asked companies to watch trial participants for side effects for two months after receiving a final vaccine dose.
Regulators for Europe, the United Kingdom and Canada are considering data as it becomes available. It is not clear when companies will submit efficacy data or when the agencies would make a decision.
Q: Could these be the first widely available coronavirus vaccines?
A: Yes, although China launched an emergency use programme 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 far along, including those from China National Biotec Group (CNBG), CanSino Biologics and Sinovac. Sinovac and CNBG have said to expect early trial data as soon as November.
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.