“You’re making incredibly important policy, policy decisions, very rapidly in a situation of uncertainty,” he said, “and there are very good reasons those decisions have to be made.” But he warned that it was difficult for scientists to reach sound conclusions based on studies of a rapid rollout of vaccines. Those evaluating the case for boosters should be “cautious” of any apparent short-term effects of a booster dose, he said.
Israeli experts told the committee that they believed a third shot of the Pfizer-BioNTech helped dampen a fourth wave of infection due to the Delta variant, which swept the nation this summer. The nation started offering boosters in late July.
Dr. Sharon Alroy-Preis, Israel’s head of public health services, described the rise in the number of hospitalized patients who had been fully vaccinated with two shots of Pfizer’s vaccine as “scary.” After offering boosters to the general population, she said, the nation is now averaging about half as many severe or critically ill patients as the Ministry of Health had anticipated.
Top federal health officials, including Dr. Anthony S. Fauci, President Biden’s chief medical adviser, have argued for weeks that immunity against infection is waning in fully vaccinated people, and that there are hints of diminished protection against more severe forms of Covid-19. Their concern, in other words, is that vaccinated people are becoming more at risk not only of getting asymptomatic or mild cases over time, but of getting sick enough to be hospitalized.
Eight of those officials in August signed a policy statement saying that boosters would be needed and that the administration was prepared to deliver them for adults as early as the week of Sept. 20, a decision some public health experts said was premature. On Friday, Dr. Vivek Murthy, the surgeon general, defended the administration’s decision to publicly announce plans for a late September rollout, emphasizing it has always been contingent on F.D.A. clearance.
“If you want to roll out booster shots to the population, you can’t flip a switch and make that happen overnight,” Dr. Murthy said at a White House briefing. “It’s important planning that has to take place with localities, with state governments, with community organizations. And so we laid out an initial plan for that purpose.”
Understand Vaccine and Mask Mandates in the U.S.
- Vaccine rules. On Aug. 23, the Food and Drug Administration granted full approval to Pfizer-BioNTech’s coronavirus vaccine for people 16 and up, paving the way for an increase in mandates in both the public and private sectors. Private companies have been increasingly mandating vaccines for employees. Such mandates are legally allowed and have been upheld in court challenges.
- Mask rules. The Centers for Disease Control and Prevention in July recommended that all Americans, regardless of vaccination status, wear masks in indoor public places within areas experiencing outbreaks, a reversal of the guidance it offered in May. See where the C.D.C. guidance would apply, and where states have instituted their own mask policies. The battle over masks has become contentious in some states, with some local leaders defying state bans.
- College and universities. More than 400 colleges and universities are requiring students to be vaccinated against Covid-19. Almost all are in states that voted for President Biden.
- Schools. Both California and New York City have introduced vaccine mandates for education staff. A survey released in August found that many American parents of school-age children are opposed to mandated vaccines for students, but were more supportive of mask mandates for students, teachers and staff members who do not have their shots.
- Hospitals and medical centers. Many hospitals and major health systems are requiring employees to get a Covid-19 vaccine, citing rising caseloads fueled by the Delta variant and stubbornly low vaccination rates in their communities, even within their work force.
- New York City. Proof of vaccination is required of workers and customers for indoor dining, gyms, performances and other indoor situations, although enforcement does not begin until Sept. 13. Teachers and other education workers in the city’s vast school system will need to have at least one vaccine dose by Sept. 27, without the option of weekly testing. City hospital workers must also get a vaccine or be subjected to weekly testing. Similar rules are in place for New York State employees.
- At the federal level. The Pentagon announced that it would seek to make coronavirus vaccinations mandatory for the country’s 1.3 million active-duty troops “no later” than the middle of September. President Biden announced that all civilian federal employees would have to be vaccinated against the coronavirus or submit to regular testing, social distancing, mask requirements and restrictions on most travel.
In its application to the F.D.A., Pfizer is asking for boosters to be given six months after the second dose, not eight months after, as President Biden called for in his booster plan last month.