A US government advisory panel has endorsed widespread use of Pfizer’s coronavirus vaccine, putting the country one step away from launching a vaccination campaign against the outbreak that has killed close to 300,000 Americans.

Vaccinations could begin within days, depending on how quickly the Food and Drug Administration signs off on the expert committee’s recommendation.

In a 17-4 vote with one abstention, the government advisers concluded that the vaccine from Pfizer and its German partner BioNTech appears safe and effective for emergency use in adults and teenagers aged 16 and older.

That endorsement came despite questions about allergic reactions in two people who received the vaccine earlier this week when Britain became the first country to begin dispensing the Pfizer-BioNTech shot.

Despite all the remaining unknowns, in an emergency, “the question is whether you know enough,” said panel member Dr Paul Offit of Children’s Hospital of Philadelphia, who concluded that the vaccine’s potential benefits outweigh its risks.

The independent review by non-government experts in vaccine development, infectious diseases and medical statistics was considered critical to boosting Americans’ confidence in the safety of the shot, which was developed at breakneck speed less than a year after the virus was identified.

The decision came as Covid-19 cases surge to ever higher levels across the US, with deaths hitting an all-time, one-day high of more than 3,100 on Wednesday.

Pfizer has said it will have about 25 million doses of the two-shot vaccine for the US by the end of December.

But the initial supplies will be reserved primarily for health care workers and nursing home residents, with other vulnerable groups next in line until ramped-up production enables shots become to widely available on demand — something that will probably not happen until the spring.

The FDA next week will review a second vaccine, from Moderna and the National Institutes of Health, that appears about as protective as Pfizer-BioNTech’s shot.

A third candidate, from Johnson & Johnson, which would require just one dose, is working its way through the pipeline. Behind that is a candidate from AstraZeneca and Oxford University.

US health experts are hoping a combination of vaccines will ultimately enable the US to conquer the outbreak.

But experts estimate at least 70% of the US population will have to be vaccinated to achieve herd immunity, the point at which the virus can be held in check.

That means it could be several months before things start to get back to normal and Americans can put away their masks.

All eyes now turn to the FDA staff scientists who will make the final decision on whether to press ahead with widespread use of the Pfizer-BioNTech vaccine.

FDA’s vaccine director Dr Peter Marks said ahead of the expert meeting that a decision would come within “days to a week”.