People familiar with the FDA deliberations say that the agency will allow 12 to 15 year olds to get third doses of Pfizer-BioNTech's vaccine on Monday.
An extra shot of Pfizer's vaccine for adolescents and adults five months after receiving a second dose is expected to be approved by regulators. Younger children with immune deficiencies would be able to get booster shots.
The decision to expand the use of the shots would come just as schools begin to reopen after the holiday break, and as governments around the world try to respond to the fast-spreading Omicron variant. Britain's National Health Service said its hospitals would build field wards to deal with the surge in coronaviruses cases, after Israel approved a fourth dose of vaccine for people with weakened immune systems.
The lives of millions of Americans were disrupted this week when several U.S. states hit their all-time case records for the coronaviruses. The C.D.C. warned potential travelers to avoid cruise travel regardless of vaccine status, after New York Mayor-elect Eric Adams vowed to keep the city's vaccine mandate for private-sector employees in place.
Health officials are trying to encourage more Americans to get a booster shot, as unvaccinated people face the greatest risk of illness and death from Omicron.
The director of the C.D.C. said that people should get their boost when they are eligible. We need more protection against Omicron because immunity is waning.
Dr. Walensky said on Wednesday that even though daily case counts had increased by 60 percent in the past week, hospitalizations and deaths were still relatively low, suggesting that Omicron might be less lethal. She and Dr. Fauci cited international research suggesting the same conclusion.
Studies have shown that the Delta variant of the Pfizer-BioNTech vaccine can cause problems for people who have not been fully vaccined, and that the two doses of the vaccine have provided strong protection.
The C.D.C. states that 70 percent of people 12 and older in the United States are fully vaccine-free. Children under 5 are not eligible for a vaccine.
There has been a rise in hospitalizations among children. Early data shows that Omicron is causing milder illness for children than it is for adults. Most of the children hospitalized with Covid-19 were unvaccinated or partially-vaccinated, according to hospital officials and physicians.
Children can be more resistant to coronaviruses, but in rare instances they can become very sick and even die. According to the C.D.C., at least 1.8 million adolescents between 12 and 15 years old have tested positive for the virus.
The studies published on Thursday showed how important vaccinations are for children and adolescents. Researchers said two doses of the vaccine reduced the risk of infections in a study of hundreds of adolescents in Arizona.
There were no serious side effects reported among children who had received the Pfizer-BioNTech vaccine, and the majority of hospitalizations were among children who had not been fully vaccineed.
The effectiveness of Pfizer's vaccine against severe illness and hospitalization was about 70% after two doses, according to a recent South African study.
Pfizer-BioNTech has a vaccine approved for use in people under the age of 18.
The vaccine advisory committee is going to meet next week to discuss the changes to the F.D.A.'s booster policy. If the committee agrees with the F.D.A., Dr. Walensky is expected to approve the revisions.
The F.D.A.'s expected decision was justified according to Dr. Kathryn M. Edwards, a vaccine expert and professor of pediatrics at the University of Tennessee.
Omicron is infecting people that have been boosted, so we have a lot of suggestions and experience with it. She said that they are not seeing a lot of severe disease. If you look at the immune responses in adults, you will see that this booster dose enhances your neutralization capacity against Omicron.
The administration's continued attention to offering boosters to younger, healthier people was misguided.
Dr. Paul Offit, the director of the Vaccine Education Center at Children's Hospital of Philadelphia and a member of the F.D.A.'s vaccine advisory committee, said that research had shown substantial and durable protection from two doses against Omicron.
He said that a booster dose could increase one's protection for several months, but that it was better to focus on the people who are already protected.
He said that the Biden administration should focus more on reaching the unvaccinated because of the overwhelming number of hospitalized children he had seen being unvaccinated.
The people familiar with the deliberations said that the F.D.A. wanted to announce its decision on Thursday, but decided to wait until Monday because Dr. Walensky wanted to hear the recommendations from the outside group. The group, which has met throughout the Pandemic to consider F.D.A. decisions, might not meet until Wednesday.
The two agencies have worked together to present a unified front in their reviews of booster shots, as they share responsibility for setting the nation's vaccine policy. The F.D.A. has been more willing to act without the advice of its outside advisory committee, with some top officials arguing that the agency needs to respond as quickly as possible in the face of the public health crisis.
The F.D.A. has not asked the outside advisory committee for recommendations before it makes decisions to expand boosters.
Dr. Walensky endorsed giving Pfizer-BioNTech booster shots to 16- and 17-year-olds without consulting her agency's expert committee. People familiar with the government's deliberations said she was unwilling to do that for younger adolescents.
The C.D.C. and the F.D.A. were accused of limiting public discussion about the evidence to justify expanding the use of boosters.
The meeting of the F.D.A. committee, which had initially been skeptical about younger, healthy people needing booster doses, could offer some transparency about the data that regulators reviewed.
He said that the American public gets to hear the discussion.
The data from Israel that showed no serious safety concerns in thousands of children who received a third dose of the Pfizer vaccine was the basis for the federal regulators' decision. There were no reports of myocarditis, a rare side effect seen mostly in younger men that has been linked to the Pfizer and Moderna vaccines. The inflammation of the heart muscle is involved.
The F.D.A. wants to allow a booster shot as early as five months after the second Pfizer dose in part because Israeli data suggests that the shorter interval is effective, according to people familiar with the government's deliberations.
The Biden administration has leaned heavily on the research of Israeli officials to make the case for Americans to get boosters.
Pfizer and its German partner, BioNTech, have both said that a third dose is needed to raise neutralizing antibodies back to a level that is effective against infections. Dr. Albert Bourla, Pfizer's chief executive, said this month that a third dose strengthens protection against Omicron.
The chief executive of BioNTech said that three doses could still offer a sufficient level of protection from disease caused by the variant.
Carl contributed to the reporting.
