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(Adds details on results of preliminary trial results on AstraZeneca/Oxford University vaccine) Nov 23 (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 more than 1.34 million lives worldwide:
Who is furthest along?
U.S. drugmaker Pfizer Inc and German partner BioNTech SE released final late-stage trial data on Nov. 18 that showed their shot was 95% effective at stopping COVID-19, the highest efficacy rate so far.
The companies are the first to publish final Phase III efficacy and safety data and plan to apply for an emergency use authorization (EUA) in the United States within days.
On Nov. 16, another U.S. pharmaceutical company, Moderna Inc , released interim data showing that its vaccine worked in a large, late-stage clinical trial with a 94.5% efficacy rate.
Interim late-stage trial results for Russia's Sputnik V vaccine published on Nov. 11 showed the shot is 92% effective.
AstraZeneca said on Monday its vaccine for the novel coronavirus, developed by Oxford University, could be around 90% effective without any serious side effects.
Johnson & Johnson says it is on track to deliver data this year.
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 got the vaccine is significantly lower than in those who received the dummy shot.
What were pharma companies waiting for to release data?
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.
Pfizer's final results were based on 170 cases within its trial involving more than 43,000 participants.
Moderna conducted its interim analysis after 95 participants developed COVID-19, while Russia's examination was conducted after 20 volunteers developed the disease.
AstraZeneca said its interim analysis was based on 131 infections among participants who received the vaccine and those in a control group who were given an established meningitis shot.