US regulators met Thursday to weigh emergency approval for a coronavirus vaccine a key medical journal deems a "triumph" as the United States logged more than 3,000 virus deaths in just one day.
With northern hemisphere countries hit by a pandemic winter surge, Britain this week became the first western country to roll out the Pfizer-BioNTech vaccine.
Canada is preparing to follow suit after also approving it.
EU countries eagerly awaited a greenlight for vaccines that the bloc's own watchdog said remained on track for approval despite a two-week-long cyberattack, which is under investigation.
Independent experts convened by the US Food and Drug Administration (FDA) discussed whether to grant emergency approval for Pfizer-BioNTech's vaccine and allow America to become the next country to move ahead with mass immunisation.
They were due to hold a non-binding vote at the end of the day and the US regulator will determine after that whether to issue an emergency use authorisation.
Momentum was building as the New England Journal of Medicine published full results of a clinical trial of the vaccine, which confirmed it was 95 percent effective with no serious safety issues.
"The trial results are impressive enough to hold up in any conceivable analysis. This is a triumph," an accompanying editorial said.
Nevertheless, the two dozen voting members of the Vaccines and Related Biological Products Advisory Committee (VRBPAC) were expected to mull outstanding issues closely in a live streamed event held over the course of the day.
These include difficult questions like when people who were on the placebo-arm of the trial should receive the vaccine, a tricky debate that weighs the need for more controlled data against paying back altruistic volunteers for their service.
The editorial that accompanied the study flagged certain "minor issues".
Questions include whether unexpected safety issues may arise when the number of people vaccinated grows to millions and possibly billions of people.
Also unknown is whether more side effects will emerge with longer follow-up, how long the vaccine remains effective, whether it will limit transmission and how it will work in children, pregnant women, and immunocompromised patients.
The FDA is likely to issue an allergy warning if it approves the vaccine following Britain's lead after two health care workers there suffered reactions and needed treatment.
The United States is the worst-hit nation in the world, with more than 15 million known infections and close to 290,000 deaths.
It registered more than 3,000 deaths in 24 hours - the highest daily toll since April.
The virus has killed at least 1,570,398 people worldwide since the outbreak emerged in China last December, according to an AFP tally from official sources.
The US hopes to vaccinate 20 million people this month, with long term care facility residents and health care workers at the front of the line. The goal is to reach 100 million by the end of February and the whole population by June.
'I'm really excited'
After Britain gave the first approved vaccine shots in the Western world, Canada also approved the Pfizer-BioNTech vaccine on Wednesday.
The first shipments to 14 sites across Canada are scheduled to arrive Monday with people receiving shots a day or two later, according to Major-General Dany Fortin, the commander put in charge of coordinating distribution.
Healthcare workers and vulnerable populations including the elderly are to be the first to receive it.
"I'm really excited. I want to get vaccinated as soon as possible, because I have a new baby," Michelle, a Toronto resident, told AFP.
Israel accepted its first shipment of the Pfizer vaccine on Wednesday, targeting a rollout on December 27.
Both Russia and China have already begun inoculation campaigns with domestically produced vaccines.
African Union plea
As European countries eagerly await vaccines, the EU's medical regulator was hit by a cyberattack in which documents related to the Pfizer vaccine were accessed, the firm said Wednesday.
The European Medicines Agency has promised to reach a decision on conditional approval for the Pfizer-BioNTech vaccine by December 29, with a ruling on Moderna's candidate to follow by January 12.
Germany, which had been hailed as a European leader in fighting the virus, saw the death toll pass 20,000 with the head of its disease control agency saying infections are taking a worrying turn.
European Central Bank chief Christine Lagarde unleashed more stimulus on Thursday to help the eurozone confront a second coronavirus wave, and warned that the outlook remained fraught with uncertainty over the pandemic's evolution and the rollout of vaccines.
At its final meeting of the year, the 25-member governing council boosted and extended their emergency measures to prop up the euro economy after a flare-up in COVID-19 cases halted a summer recovery and forced another round of restrictions.
But while wealthier nations have the financial and logistical abilities to roll out the vaccines, there are concerns that the poorer - and more vulnerable - parts of the world will be left behind.
African Union chairman Moussa Faki Mahamat said Wednesday that "those who have the (financial) means must not monopolise the vaccines".