Pfizer’s Covid-19 vaccine passed a critical milestone on Thursday when a panel of experts formally recommended that the Food and Drug Administration authorize the vaccine. The agency is likely to do so within days, giving health care workers and nursing home residents first priority to begin receiving the first shots early next week.

The F.D.A.’s vaccine advisory panel, composed of independent scientific experts, infectious disease doctors and statisticians, voted 17 to 4, with one member abstaining, in favor of emergency authorization for people 16 and older. Although the F.D.A. does not have to follow the advice of its advisory panel, it usually does.

WASHINGTON — The coronavirus vaccine made by Pfizer and BioNTech provides strong protection against Covid-19 within about 10 days of the first dose, according to documents published on Tuesday by the Food and Drug Administration before a meeting of its vaccine advisory group.

The finding is one of several significant new results featured in the briefing materials, which include more than 100 pages of data analyses from the agency and from Pfizer. Last month, Pfizer and BioNTech announced that their two-dose vaccine had an efficacy rate of 95 percent after two doses administered three weeks apart. The new analyses show that the protection starts kicking in far earlier.