Some American adults with weakened immune systems who received a third dose of either the Pfizer-BioNTech or Moderna coronavirus vaccine authorized just for them will become eligible for a fourth shot as a booster next year, according to updated guidelines from the Centers for Disease Control and Prevention.“In such situations, people who are moderately and severely immunocompromised may receive a total of four vaccine doses,” with the fourth coming at least six months after the third, the C.D.C.’s guidelines said.In August, federal regulators cleared a third dose of the Pfizer-BioNTech and Moderna vaccines for some immunocompromised recipients of those vaccines, instructing them to get it at least 28 days after their second shot. Federal agencies said that studies have shown that those people may not be adequately protected by just two shots.The earliest that immunocompromised people who received that third mRNA vaccine shot can get a fourth shot as a booster would be February. The agency said that people could select that booster from any of the three coronavirus vaccines available in the United States.The C.D.C. also recommends that moderately and severely immunocompromised adults who received Johnson & Johnson’s one-dose vaccine get another dose of any one of the three vaccine brands, at least two months after their initial shot.The agency updated its guidelines on Monday, adding the possibility of a booster dose for many immunocompromised people, including those undergoing chemotherapy, recovering from a solid organ transplant or facing certain other medical issues, like infection with H.I.V.The new recommendations also specified that a fourth dose of Moderna’s vaccine should be half the size of a normal dose.Many health officials and experts in the United States and other countries have made a distinction between additional shots for immunocompromised people, who may not have mounted a strong immune response after their initial doses, and broader booster programs intended to shore up other peoples’ immunity, which can wane against infection naturally over time.The World Health Organization has supported additional doses for people with weakened immune systems while calling for a global moratorium until the end of the year on booster programs for otherwise healthy people, so that more doses can be allocated to lower-income countries with low rates of vaccination.The call for a moratorium has not stopped countries like Israel, the United States and Germany from moving ahead with booster programs.

School may still seem blissfully far off for American students in the midst of summer. But for many who are eligible, time may be running out for a back-to-school necessity: getting fully vaccinated against the coronavirus before classes resume.Many of the country’s more than 13,000 districts, especially in the South and Southwest, plan to start the 2021-22 school year well before Labor Day. Completing a course of Pfizer-BioNTech’s vaccine, the only vaccine now federally authorized for 12- to 17-year-olds, takes at least five weeks for the two shots to be administered and full protection to be reached. In many of those early-starting districts, students would need to get their first dose in the next few days to be fully immune in time.In the Hamilton County School District in Tennessee, the first day of school is scheduled for Aug. 12. Counting back from then, students would have to get their first shot no later than Thursday to be fully protected by opening day.Cody Patterson, a spokesman for the district, which encompasses Chattanooga and serves 45,000 students, said that while vaccinations are not mandatory for the new school year, the district was making clear to parents “that we believe vaccination is a key strategy to keeping school open.”Mr. Patterson said that individual schools in the district would probably accommodate students case by case if they are worried about finishing their vaccinations.Schools across the country closed and switched to online instruction when the pandemic took hold last year. But as the pandemic wore on, research showed that elementary and secondary schools were not major drivers of infection.Colleges are another matter, with a number of outbreaks seen on campuses. Many colleges (along with some private secondary schools) are requiring vaccinations for students to attend in person this fall. It’s harder for public middle and high schools to do that, for legal and other reasons, and a spokesman for the American Federation of Teachers said the union was not aware of any U.S. school district that is mandating vaccinations.It has only been since May that any vaccine was available for 12- to 15-year-olds in the United States. In many states, teenagers need parental consent to be vaccinated. No vaccine has yet been authorized for children under 12.Michael Poore, the superintendent of the Little Rock School District in Arkansas, said that the district had contacted parents, worked with local health authorities and done extensive outreach on local and social media to persuade students and their parents to get a vaccine.The district also ran vaccination events at its 11 middle and high schools, he said, but only 300 to 400 of the district’s roughly 11,000 eligible students got shots at the events.School in Little Rock starts on Aug. 16, so to be fully protected by then, students would have to get their first dose by Monday.“We’re really going to push the vaccines in August,” Mr. Poore said, “because if you haven’t had the shot and you’re in close proximity to someone who has the virus, you’re going to have to be quarantined.”It is already too late for not-yet-vaccinated students to get fully protected before school starts in some places, like the Chandler Unified School District in Arizona, which reopens July 21.Kimberly Guevara, a district spokeswoman, said the district had informed parents when the vaccine was authorized for teenagers and told them how to get a shot, but “we’re not going to force vaccinations on students.”Ms. Guevara said she and the eligible members of her family got vaccinated as soon as they could.

Parents and unpaid caregivers of adults in the United States reported far higher rates of mental health issues during the coronavirus pandemic than people who held neither of those roles, federal researchers reported on Thursday.About 70 percent of parents and adult caregivers — such as those tending to older people, for example — and about 85 percent of people who were both reported adverse mental health symptoms during the pandemic, versus about a third of people who did not hold those responsibilities, according to new research by the Centers for Disease Control and Prevention.The study also found that people who were both parent and caregivers were eight times more likely to have seriously considered suicide than people who held neither role.“These findings highlight that parents and caregivers, especially those balancing roles both as parents and caregivers, experienced higher levels of adverse mental health symptoms during the Covid-19 pandemic than adults without these responsibilities,” the authors said.“Caregivers who had someone to rely on for support had lower odds of experiencing any adverse mental health symptoms,” they said.The report follows innumerable anecdotes and several studies suggesting spikes in mental health problems among parents and caregivers during the pandemic. But the new C.D.C. report noted that “without prepandemic mental health data in this sample, whether adverse mental health symptoms were caused by or worsened by the pandemic is unknown.”The study is based on data from online English-language surveys administered to panels of U.S. residents run by Qualtrics, a company that conducts commercial surveys, for the Covid-19 Outbreak Public Evaluation Initiative, an effort to track American attitudes and behaviors during the pandemic. The data was gathered from Dec. 6 to 27 last year, and from Feb. 16 to March 8 of this year, and relied on 10,444 respondents, weighted to match U.S. demographic data, 42 percent of whom identified as parents or adult caregivers.The study noted that the results might not fully represent the U.S. population, because of factors like the surveys only being presented online and in English.The surveys included screening items for depression, anxiety, Covid-19 trauma and stress-related disorders, and asked respondents whether they had experienced suicidal thinking in the past month. About half of the parent-caregivers who responded said that they had recently had suicidal thoughts.Elizabeth A. Rohan, a health scientist at the C.D.C. and one of the study’s authors, said in an interview that what set this research apart was a large sample size and a broad definition of caregiver, which allowed for a more inclusive picture of people in that role.“Our net captured more people than other surveys,” Dr. Rohan said.Dr. Rohan said that the study reinforced the need to destigmatize mental health issues among caregivers and for better support systems. Communication is key, she said, and “it doesn’t have to be professional help.”She added, “We cannot underestimate the importance of staying connected to one another,” which is helpful whether the person is “a trusted friend, a family member or a professional.”If you are having thoughts of suicide, call the National Suicide Prevention Lifeline at 1-800-273-8255 (TALK). You can find a list of additional resources at SpeakingOfSuicide.com/resources.

Vermont has at least partially vaccinated 80 percent of residents 12 or older, allowing it to lift all remaining state pandemic restrictions, Gov. Phil Scott announced on Monday.Federal data confirmed that the state passed the 80 percent milestone first, while lagging vaccination rates elsewhere have imperiled President Biden’s national goal of getting shots into the arms of at least 70 percent of adults over 18 by July 4.“I’m very proud to announce that Vermont has now become the first state in the nation to vaccinate over 80 percent of its 12-and-over population,” Mr. Scott said at a news conference on Monday.Vermont has been very successful at handling the coronavirus. A New York Times database shows that the state has reported fewer cases and fewer deaths, relative to its population, than any state but Hawaii. Vermont has vaccinated 83 percent of its adult population, aged 18 or older; Hawaii and Massachusetts are the only other states so far that have exceeded 80 percent by that measure.“Not only do we lead the United States, but Vermont is now a global leader in vaccinations to defeat Covid-19,” Mr. Scott said. “Our state has shown the world what’s possible when you have a group of people with the right attitude following the data and trusting medical science.”The number of new positive tests reported daily across the country seems to be leveling off after having fallen steadily for months. Experts are worried that states with low rates of vaccination, particularly in the South, could incubate new outbreaks.Mr. Scott, a Republican, lifted his state’s mask mandate and capacity restrictions for vaccinated people on May 14. He said that Vermont’s state of emergency would end on Tuesday.“It’s really very simple: There are no longer any state Covid-19 restrictions,” he said.People in Vermont still have to abide by federal pandemic regulations, and businesses will be allowed to take safety measures like requiring masks if their owners choose to do so, he said.“This is something that businesses have to decide for themselves,” Mr. Scott said.Many states have relaxed or removed most of their pandemic restrictions, including some with far lower vaccination rates than Vermont’s.Mr. Scott praised public health officials for his state’s testing program and vaccine rollout. But he noted that Vermont’s work was far from done.“We’ll continue to vaccinate as many Vermonters as possible, because every shot given today, tomorrow and in the weeks to come is just as important as the ones we administered yesterday,” he said.Amy Schoenfeld Walker contributed reporting.

Moderna on Tuesday became the next pharmaceutical company to apply to the U.S. Food and Drug Administration for full approval for its coronavirus vaccine for use in people 18 and older.Last month Pfizer and BioNTech applied to the agency for full approval of their vaccines for use in people 16 and older.“We look forward to working with the F.D.A. and will continue to submit data from our Phase 3 study and complete the rolling submission,” Stéphane Bancel, Moderna’s chief executive, said in a statement.Moderna’s vaccine was authorized for emergency use in December, and as of Sunday, more than 151 million doses had already been administered in the U.S., according to data from the Centers for Disease Control and Prevention.Moderna announced last week that its vaccine appeared to be highly effective in teenagers and that it planned to apply for emergency use authorization for adolescents in June. Pfizer’s vaccine was authorized for use in 12- to 15-year-olds last month.Both the Moderna and Pfizer vaccines require two shots spaced several weeks apart, and are built around messenger RNA, the genetic material that cells read to make proteins, to help generate antibodies to the virus.Full approval for each of the vaccines would allow the companies to market them directly to consumers and could make it easier for schools, employers and government agencies to require them. It could also encourage the U.S. military, which has had low uptake of vaccines, to mandate vaccinations for service members.Approval could also help raise public confidence in another vaccine, after the pace of vaccinations has dropped sharply since mid-April.A recent poll from the Kaiser Family Foundation showed signs that some hesitant people have been persuaded: About a third of people who had planned to “wait and see” whether they would get vaccinated said that they had made vaccine appointments or planned to do so.“I think there are many people who were on the fence, who were worried about things moving too rapidly and about possible side effects,” said Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases and a vaccine expert. “But those concerns are being allayed as they see more of their friends and acquaintances celebrating getting vaccinated.”Jan Hoffman contributed reporting.

All state-run mass vaccination sites in New York will allow anyone 16 or older to walk in without an appointment and get their first dose, beginning on Thursday, Gov. Andrew M. Cuomo announced on Tuesday.Walk-in vaccinations will be available at state-run sites in New York City, like the Javits Center in Manhattan and Yankee Stadium in the Bronx, as well as on Long Island and in upstate cities like Albany and Syracuse, the governor said.Second doses will still be given by appointment, which will be scheduled after the first dose is administered.“Just show up, and roll up your sleeve, and the mass vaccination sites have the capacity to handle it,” Mr. Cuomo said at a news conference on Tuesday.Other kinds of vaccine providers in the state, like pharmacies and sites run by cities and counties, will have the option to start allowing walk-ins as well, a step the governor encouraged.New York had already begun allowing some vaccinations without prior appointments. Mr. Cuomo announced last week that people 60 and over could walk in for vaccination at 16 state-run sites. And Mayor Bill de Blasio of New York City announced last week that city-run vaccination sites would let anyone eligible walk in for a shot.Allowing walk-ins simplifies a process that bedeviled many New Yorkers earlier in the pandemic, when obtaining a vaccine appointment often took hours of online searching and some luck as well. The new policy may also draw out people who are still hesitant to get vaccinated, Mr. Cuomo said.“This is our way of saying, if you were intimidated by the process of trying to make an appointment, that’s gone,” the governor said. He said it was feasible to allow more walk-ins because fewer vaccinations were being administered across the state now — about 115,000 doses a day — than a few weeks ago, when the state peaked at about 175,000 doses a day.“The demand is reducing, fewer people are asking for appointments,” Mr. Cuomo said.State data show that just under 45 percent of New York residents, or just over 8.9 million people, had received at least one dose of the vaccine by Tuesday morning.Reports of new Covid-19 cases and hospitalizations have declined in the state, according to a New York Times database, but the risk of infection still remains very high in New York City, where some troublesome variants of the virus appear to be on the rise.