The World Health Organization, which has been resistant to endorse the wide use of booster shots and slow in recommending vaccinations for children, moved on Friday to revise its advice on both fronts, bringing its guidance closer to that of most wealthy nations, including the United States.
An advisory panel for the agency recommended expanding the use of a reduced dosage of the Pfizer-BioNTech vaccine to children aged 5 to 11. It also recommended that frontline health care workers, older adults and those in other high-risk groups who have been inoculated be offered a booster dose four to six months after their initial doses.
The committee had already authorized boosters for those whose immune systems are diminished.
As many nations — fearing waning immunity and new waves of infection — began rolling out booster campaigns, the W.H.O. has warned that those efforts could undermine ones to get much-needed vaccine supplies to poorer countries.
Roughly 60 percent of the world’s population has received at least one dose of a Covid vaccine, but only 9.4 percent of people in low-income countries have received at least one dose, according to Our World in Data.
In August, before the Omicron variant had been identified, the W.H.O. called for a global moratorium on boosters to increase the distribution of vaccine supplies to countries in the greatest need. But Omicron has once again scrambled efforts to get ahead of the virus, and there is a growing body of evidence that suggests that older people can benefit from booster shots.
The C.D.C. released data on Thursday that suggested that the risk of hospitalization for unvaccinated Americans ages 50 to 64 with Covid was far higher than it was for those in the age group who were vaccinated and received a booster shot.
Dr. Katherine O’Brien, director of the W.H.O.’s department of immunization, vaccines and biologicals, said that the agency’s new guidance was in line with its central goal — to protect people who are at the highest risk of severe disease and of death.
But the agency is still not going as far as many wealthy nations, which are now offering boosters to all adults. In the U.S., the C.D.C. recently went farther, endorsing booster shots of the Pfizer-BioNTech vaccine for children ages 12 and older.
Dr. Soumya Swaminathan, the W.H.O.’s chief scientist, said Tuesday that “there’s no evidence right now” that healthy children and teenagers need an extra dose, adding that the aim of the booster program is to protect “those at highest risk of severe disease and dying.”