LONDON — Britain could become the first Western country to approve a coronavirus vaccine, with the highest hopes resting on Pfizer's candidate and the homegrown offering from Oxford University and AstraZeneca.

Those hopes persist, accompanied by much flag waving, despite questions about the Oxford vaccine’s trials and effectiveness.

Britain, like other countries around the world, urgently wants to save lives and stop outbreaks. But it also wouldn’t mind credit for being the first to launch a massive immunization campaign after a rigorous review.

Russia and China are already widely distributing their own vaccines, though they have been less transparent about their process.

Britain’s drug regulators are known to be tough but nimble. They have declined to confirm the ambitious timelines floated by some officials that a vaccine could be distributed for use in the first weeks of December. In all their communiques, they promise that “the safety of the public will always come first.”

But the British government and the vaccine developers have their feet on the gas.

“This could — could, if we’re lucky, if everything goes right — be available just in a few weeks,” Prime Minister Boris Johnson said Monday during a tour of a laboratory in Wrexham, Wales, where the AstraZeneca vaccine is being manufactured.

On Friday, the government asked its regulator to begin to consider AstraZeneca’s vaccine for emergency approval. Pfizer, which reports that its vaccine is 95 percent effective, submitted its own data for regulatory review earlier in the week.

“We have already started our analysis and will aim to make a decision in the shortest time possible, without compromising the thoroughness of our review,” June Raine, chief executive of the Medicines and Healthcare Products Regulatory Agency, said in a statement.

Britain’s National Health Service has advised the chief executives overseeing the system’s hospitals and clinics that they could be receiving vaccine doses as soon as “early December.”

That would be a quicker timeline than in the United States or the European Union. The U.S. Food and Drug Administration has indicated that it won’t make a regulatory decision before Dec. 10, and the E.U.’s regulator has talked about earliest approval coming “towards the end of this year or the beginning of next.”

British regulators are also considering a vaccine from the American company Moderna, with a reported 94 percent efficacy in trials. But U.K. officials have said the earliest that vaccine would be available in Britain and wider Europe would be in the spring.

Penny Ward, a visiting professor in pharmaceutical medicine at King’s College London, said she wouldn’t be surprised if British approval for one of the leading vaccines came before approval in the United States.

The U.K. regulator, she said, “has always been extremely efficient — and exacting.” She said that in normal times, “once you filed a dossier, you’ll have an answer in six weeks, so they are fast.” She said the U.S. approval system, in her experience, is slower.

In addition to cheering for speedy vaccine approval, British officials have been giddy that the AstraZeneca vaccine is from the “home team.” The prime minister has praised the “brilliant scientists” at Oxford University and said their work “has the makings of a wonderful British scientific achievement.”

His office denied reports in the British media that it wanted the vaccine’s packaging to include the Union Jack, the flag of the United Kingdom. 

While Britain has diversified its investments in vaccines, its biggest bet has been on Oxford-AstraZeneca, with a preorder of 100 million doses. The government has also ordered 40 million doses from Pfizer and its German partner, BioNTech. It has placed an order for a further 7 million doses from Moderna.

Of the three, the Oxford vaccine will be cheapest and easiest to distribute, because it doesn’t require special freezers and can be stored long-term at standard refrigerator temperatures. But there are questions about whether it will prove as effective.

AstraZeneca last week said its interim data showed the vaccine to be 70 percent effective overall, with the most promising results — a 90 percent effective vaccine — reported in a group of fewer than 3,000 people who received only half the initial dose of the two-dose protocol. The full two-dose regimen, the one being tested in a large clinical trial in the United States, was 62 percent effective.

Those results — announced via news release and a news conference on Zoom — produced some confusion. The scientists did not explain how some volunteers got half-doses.

Afterward, Mene Pangalos, head of AstraZeneca’s non-oncology research and development, told Reuters, “The reason we had the half dose is serendipity.”

Pangalos said administration of the half-dose regime, at first, was “a mistake.” The study team immediately alerted the authorities, and it was decided to continue the trial.

But Sarah Gilbert, a leader of the Oxford vaccine program, seemed to push back on the assertion of any error, adding to the confusion. “It wasn’t a mix-up in dosing,” Gilbert told the Financial Times on Friday. “It’s quite usual to look at different dose levels when we do vaccine trials.”

The Oxford researchers have submitted their data to a medical journal, they say, and it may be published later this week.

Ward, of King’s College, noted that even at the lower levels of effectiveness, the Oxford jab exceeds the 50 percent threshold that health regulators in Britain, the United States and Europe had set.

“The objective is not the entire prevention of any illness whatsoever,” she said, “but rather prevention of severe illness requiring hospital treatment, which carries higher mortality. And the Oxford vaccine, at both doses, does that.”

She expressed concern that the suggestion of a mistake in the trials “has been magnified into ‘it doesn’t work.’ ”

“It was all one could do not to put one’s head in one’s hands, really, and sigh,” she said.

It is unclear whether the questions raised over the interim results from AstraZeneca will dampen enthusiasm for rolling up sleeves.

On Saturday, police clashed with anti-vaccine and anti-lockdown protesters, most of whom were not wearing masks, in central London. Video posted on social media showed chaotic scenes, with protesters throwing bottles and smoke bombs. More than 150 people were arrested.

More worrying for public health officials than strident vaccine opponents are the “vaccine hesitant,” who may be wary of the shot, especially if they fear that corners were cut on safety.

To coax them along, Britain’s National Health Service is considering deploying celebrities who are “known and loved,” and “influencers” with big social media footprints, to help persuade Brits to take a vaccine, the Guardian newspaper reported. The paper said members of the royal family and soccer players were thought to be “ideal recruits.”

Till Bruckner, founder of the clinical-trial transparency advocacy group TranspariMED, said that releasing partial results via news release was partly to blame.

“No one will start to vaccinate based on a press release, so why this crazy urge to release partial results in a press release?” he asked. “Then you have investors, journalists, medical professionals asking questions, a series of briefings. . . . What’s the value added?”

Carolyn Y. Johnson in Boulder, Colo., and Quinten Aries in Brussels contributed to this report.