WASHINGTON — The Food and Drug Administration said early Friday that it “will rapidly work toward” authorization of the Pfizer-BioNTech coronavirus vaccine on an emergency basis, an action that would kick off an unprecedented effort to inoculate enough Americans to stop a rampaging pandemic.

The FDA statement, which came hours after federal advisers endorsed the vaccine, added that the agency had also notified the Centers for Disease Control and Prevention and Operation Warp Speed, “so they can execute their plans for timely vaccine distribution.”

But the prospect of relief from the coronavirus came as 107,000 people were hospitalized with COVID-19, the disease caused by the virus, and a record 3,347 deaths were reported by state health departments, topping the milestone reached one day earlier. Within days, the country will likely surpass 300,000 deaths since the pandemic’s arrival.

The worsening situation has riveted attention on the final steps of the vaccine approval process. The thumbs’ up from the FDA’s vaccine advisory committee was the culmination of an all-day meeting during which the panel heard presentations on the safety and effectiveness of the vaccine, including plans to monitor its longer-term safety.

The key moment came just after 5:30 p.m., when the agency asked its independent advisers: “Based on the totality of scientific evidence available, do the benefits of the Pfizer-BioNTech COVID-19 Vaccine outweigh its risks for use in individuals 16 years of age and older?”

The committee voted yes, 17 in favor, four against and one absention.

Panel members did not have an opportunity to explain their votes, but at least two dissenters objected to inclusion of 16- and 17-year-olds, given what they described as the low risk of severe disease in that age group and how few had participated in the trial.

“I would have voted ‘yes’ most enthusiastically had the language been ‘ … 18 years of age and older,’ ” said David Kim, director of the division of Vaccines in the Office of Infectious Disease and HIV/AIDS Policy in the Department of Health and Human Services.

Those arguments were vehemently disputed by panel member Paul Offit, a pediatrician and vaccine expert at the Children’s Hospital of Philadelphia. “Kids in our hospital have had cardiac anomalies,” he said. “We have clear evidence of benefit and all we have on the other side is theoretical risk.”

When the FDA follows with an emergency authorization, the shots will start being moved to the states within 24 hours, according to officials at Operation Warp Speed, the Trump administration’s effort to accelerate the development and delivery of vaccines. Inoculations could begin early next week.

After the FDA authorization, an advisory committee to the CDC will vote on whether to recommend the vaccine and for which groups. First in line to be inoculated are health care personnel and residents and staff of long-term care facilities, according to its previous recommendations. But states will have the final say on who gets the first shots and where they are administered. Those considerations are complicated by extreme logistics challenges, including the sub-Antarctic storage temperatures the vaccine requires.

The two-shot vaccine, which has been shown to be 95 percent effective in randomized trials involving thousands of people, has already been approved by the United Kingdom, Canada, Bahrain and Saudi Arabia. U.S. officials, however, have hewed to a more rigorous approval process that they believe will boost confidence in the vaccine among the general public. Surveys show many people in the U.S. remain unsure about the safety of the vaccines and whether they will get the shots.

“The American public demands and deserves a rigorous, comprehensive and independent review of the data,” said Doran Fink, deputy director of the FDA’s Division of Vaccines and Related Products. “That is what FDA physicians and scientists, all of us career public health servants, have been doing over days, nights, weekends and, yes, over the Thanksgiving holiday.”

A sense of urgency hung over the hearing. Kathrin Jansen, Pfizer’s head of vaccine research and development, told the panel that “with the high efficacy and good safety profile shown for our vaccine, and the pandemic essentially out of control, vaccine introduction is an urgent need.”

Still, the vaccine is coming too late to eliminate a staggering loss of life anticipated this winter, CDC Director Robert Redfield said Thursday to the Council on Foreign Relations. “We are in the time frame now that, probably for the next 60 to 90 days, we’re going to have more deaths per day than we had at 9/11 [terrorist attacks] or we had at Pearl Harbor,” he said.

During the meeting, committee members pressed the FDA on the vaccine’s safety, raising questions about adverse reactions reported Wednesday when British regulators ordered hospitals to avoid giving the shots to people with a history of “significant” allergic reactions. That directive came after two health care workers had severe reactions after receiving the first dose of the vaccine, which British regulators authorized last week. British authorities said both workers have a history of serious allergies.

Susan Wollersheim, a medical officer in the FDA’s Office of Vaccines Research and Review, said the FDA has asked Pfizer to monitor vaccine recipients for “anaphylactic reactions” as a potential risk following the British report.

Much remains unknown about the cases in the United Kingdom, and experts said more data was urgently needed. A specific study could be done to see if the vaccine carried risk to people with severe allergies – data that might be essential to overcome concerns from Americans who heard alarming news reports.

“There are tens of millions of people in this country that carry EpiPens because they have peanut allergies and egg allergies,” Offit said. “They are going to believe that they can’t get this vaccine. That is a lot of people.”

In its review, the FDA found a slightly higher number of adverse events – “potentially representing allergic reactions” – in the group that received the vaccine, compared with those who got the placebo. There were 137 “hypersensitivity-related” reactions to the vaccine, compared with 111 such events in the placebo group. But there were no cases of anaphylactic reactions in the trial.

Pregnant women have been excluded from coronavirus vaccine trials, but the FDA’s limited data suggests no specific risk to pregnant women or a fetus. Fink said the agency is expecting results later this month from a developmental and reproductive study in animals that could help elucidate risks, but said the agency will likely allow pregnant women and their doctors to decide whether to take the vaccine.

An authorization for Pfizer-BioNTech is the first of what health experts hope will be several vaccines to cross the finish line. Next to be considered is Moderna’s vaccine. The FDA will release its assessment of that vaccine on Tuesday and the advisory committee will review it on Dec. 17. If it gets favorable evaluations, as expected, the FDA is likely to authorize that vaccine within days.

Between the two vaccines, government officials project having 40 million doses by year’s end – enough to fully vaccinate 20 million people with the two-shot regimen.

Despite the committee’s consensus that the vaccine is safe and effective, there was at least one cautionary note about the absence of long-term data. A. Oveta Fuller, associate professor of microbiology and immunology at the University of Michigan, voted against the recommendation, expressing concerns about the lack of long-term safety data for a vaccine technology not used before in humans.

She called the risk “limited” but predicted “the uptake in the community is going to be very poor.”

The panel also engaged in extensive debate over how to handle the difficult issue of when to give participants who received a placebo access to the vaccine. Some participants have called for it, but the FDA has expressed concerns that “unblinding” the continuing trial could hurt efforts to collect longer-term safety data.

Pfizer officials on Thursday proposed to the FDA that participants in the placebo group would be allowed to access the vaccine when they become eligible under guidelines for the general public. Those guidelines are being issued by federal, state and local governments.

In preparation for the meeting, the FDA on Tuesday published a 53-page evaluation saying the vaccine appears to meet the standards it laid out in recent months for emergency authorization. The agency has said a vaccine must be at least 50 percent effective; its own scientists confirmed Pfizer’s assessment that the vaccine regimen was 95 percent effective at preventing the coronavirus in a large clinical trial.

On safety, the FDA found that the vaccine has “a favorable safety profile, with no specific safety concerns identified that would preclude issuance of an [emergency authorization].” The vaccine caused several side effects, including sore arms, fatigue, headaches, muscle pain and chills, but they typically disappeared after a day or two. Pfizer provided the agency with a median of two months of follow-up on 38,000 participants in the trial.

The one surprise in the report was that the first shot in the two-dose regimen was 52 percent protective against the coronavirus in the three weeks between the two shots. But the FDA noted that there wasn’t enough data to draw firm conclusions about the efficacy of a single shot. Government officials have said they plan to hold back supplies for the second shots, which must be given three weeks later, to ensure sufficient supply of the shot that provides people get complete protection. But the signal of early protection from a single dose has raised questions about whether that’s the best way to use limited doses amid surging cases.

During the portion of the FDA’s advisory committee meeting for the general public, some expressed concerns about green lighting a vaccine that was so rapidly developed and reviewed. Others like Evan Fein expressed strong support.

Fein told the panel he was a clinical trial participant at New York University and strongly urged quick action.

He said he is certain he got the vaccine last summer – not a placebo – because he had fatigue, fever and muscle aches after the second shot. But he said there were no longer-term side effects.

He said it would be “immoral and unethical” to not authorize the vaccine.