Scientific advisers to the Centers for Disease Control and Prevention will meet on Thursday to debate whether to recommend a third dose of the Pfizer-BioNTech vaccine to children ages 5 to 11.

The Food and Drug Administration authorized the booster shot for this age group on Tuesday. The C.D.C.’s advisers are also expected to endorse the shots. Dr. Rochelle Walensky, the agency’s director, is expected to sign off quickly on the recommendation.

The extra dose may boost immunity to the current Omicron variants in these children. Studies have shown that two doses of the vaccine offer virtually no barrier against infection with the Omicron variant in children ages 5 to 11, although protection against severe disease remains strong.

In adolescents ages 12 to 17, two doses offered little protection even against hospitalization, but a booster shot significantly improved immunity.

Pfizer and BioNTech reported on Tuesday that in children ages 5 to 11, a third dose generated antibodies against both the Omicron variant and the original version of the coronavirus. In a clinical trial, the children received 10 micrograms of vaccine — one-third of the dose given to adolescents and adults — in each shot.

As with the first two doses, the booster shot appeared safe, the companies reported. The most commonly reported side effects were pain, redness and swelling at the injection site, as well as aches, chills and fever.

Fewer than one-third of 5- to 11-year-olds in the United States have received two doses. Many parents have hesitated to immunize their children, in part because they are at much lower risk of severe disease than adults.

But record numbers of children were hospitalized during the Omicron surge this winter. And some studies suggest that even children who have a mild illness may experience symptoms for months.