Federal regulators evaluated for the first time on Friday the safety and efficacy of a coronavirus vaccine for children 5 to 11, saying that the benefits of staving off Covid-19 with the Pfizer-BioNTech vaccine generally outweighed the risks of the most worrisome possible side effects in that age group. The analysis came on the same day that the Food and Drug Administration posted data from Pfizer showing that the vaccine had a 90.7 percent efficacy rate in preventing symptomatic Covid-19 in a clinical trial of 5- to 11-year-olds.

The findings could add momentum for F.D.A. authorization of the pediatric dose on an emergency basis, perhaps as early as next week