Covid-19: C.D.C. Says Hospitalizations for Children Are Rising as Delta Surges

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Pediatric hospitalizations for Covid-19 have soared over the summer as the highly contagious Delta variant spread across the country, according to two new studies from the Centers for Disease Control and Prevention.

From late June to mid-August, hospitalization rates in the United States for children and teenagers increased nearly fivefold, although they remain slightly below January’s peak, one new study found.

But vaccination has made a difference. During this summer’s wave, the hospitalization rate was 10 times as high in unvaccinated adolescents as in those who were vaccinated, researchers found. Pediatric hospital admissions were nearly four times as high in states with the lowest vaccination rates as in those with the highest rates, according to a second study.

The studies, released on Friday, do not provide clear answers about whether Delta causes more severe disease in children than earlier versions of the virus. The rise in pediatric hospitalizations could also be because of the variant’s high infectiousness.

Indeed, one study concluded that the proportion of hospitalized children with severe disease had not changed in late June and July, when the Delta variant became dominant in the United States.

The rates reported in the C.D.C. studies are based on data from two national surveillance systems, including hospitals in 49 states and Washington, D.C.

In one C.D.C. study, researchers found that since July, when the Delta variant became predominant, the rate of new coronavirus cases increased for children 17 or younger, as did Covid-related emergency room visits and hospital admissions.

“We saw that E.R. visits, cases and hospital admissions are rising,” said Dr. David Siegel, lieutenant commander in the U.S. Public Health Service and the lead author of the paper. “It could be that Delta is more severe or that Delta is more transmissible, and it could be related to other factors such as masking.”

The study also found that Covid-related emergency room visits and hospital admissions among children were more than three times as high in states with the lowest vaccination coverage compared with states with high vaccination rates, underscoring the importance of communitywide vaccination to protect children. Other important factors that might affect regional differences included masking and social distancing measures, the study noted.

Last month, as Delta surged, the incidence of Covid in children rose from earlier in the summer — reaching 16.2 cases per 100,000 children ages 4 or under; 28.5 cases per 100,000 children ages 5 to 11; and 32.7 cases per 100,000 children ages 12 through 17.

That rate represented a sharp spike from a June low of 1.7 per 100,000 children ages 4 or under; 1.9 cases per 100,000 children ages 5 to 11; and 2.9 per 100,000 children between ages 12 and 17. It was still below the peak incidence of cases among children last January.

The proportion of Covid patients under 17 who were admitted to intensive care units ranged from 10 to 25 percent from August 2020 through last June, and hovered at 20 percent by July 2021, according to the C.D.C. study.

In a second study, researchers analyzed data from the Covid-Net surveillance network, which includes information on hospitalizations in 99 counties across 14 states.

Over the course of the pandemic — or from March 1, 2020, to Aug. 14, 2021 — there were 49.7 Covid-related hospitalizations per 100,000 children and adolescents, the researchers found.

But the weekly rates have been climbing since July. During the week ending Aug. 14, there were 1.4 Covid-related hospitalizations for every 100,000 children, compared with 0.3 in late June and early July. (That remains slightly below the peak weekly rate of 1.5 hospitalizations per 100,000 children, in early January 2021, in the post-holiday wave of cases.)

Hospitalization rates have increased most sharply for children who are 4 or younger. In the week ending Aug. 14, there were 1.9 hospitalizations per 100,000 children in that age group, nearly 10 times as many as in late June.

But based on the limited data available so far, it does not appear that the Delta variant is affecting the incidence of severe disease or deaths among children, which have been somewhat steady and relatively low throughout the pandemic.

Among the children and adolescents hospitalized from June 20 to July 31, 23.2 percent were admitted to the I.C.U., 9.8 percent required mechanical ventilation and 1.8 percent died. Those figures were roughly the same as those for children who were hospitalized before the Delta variant became widespread.

As another wave of coronavirus cases and hospitalizations rises in parts of Canada, its public health agency is urging young people, a lagging demographic in the country’s vaccination campaign, to roll up their sleeves.

In a new analysis released on Friday, the Public Health Agency of Canada said that there was an “urgent need” to increase vaccinations among Canadians aged 18 to 39 to reduce the risk that hospitals will become overwhelmed. It noted that there was an immediate “window of opportunity” to slow transmissions.

Sixty-eight percent of all Canadians are fully vaccinated, and 75 percent have received at least one dose, according to The New York Times database. By comparison, only 53 percent of Americans are fully vaccinated and 62 percent have received at least one dose.

Among those Canadians eligible for the vaccine, aged 12 and over, 77 percent are fully vaccinated. However, the rate is much lower for people in their 20s and 30s. Health officials say about 63 percent of people aged 18 to 29 have received both doses, while 68 percent of adults in their 30s are fully inoculated.

As it has in other countries, the highly contagious Delta variant has driven up cases and hospitalizations in Canada in recent weeks. On Thursday, the seven-day average of new cases in Canada was 3,489, up 56 percent from two weeks earlier, according to the Times database. Deaths rose 8 percent over the same period.

Hospitalizations were also up 34 percent over the last week and were dominated by unvaccinated patients, the country’s chief public health officer, Dr. Theresa Tam, said in a statement.

The upward trend could climb to more than 15,000 cases a day by October if vaccination rates don’t rise, the agency’s modeling showed. But, the increase in cases could also be curbed if other public health measures succeed in reducing transmissions by 25 percent, the agency said.

Some provinces could achieve this by restricting access to a number of public settings to the fully vaccinated. Both Quebec and Manitoba began vaccine passport systems this week, requiring individuals to present an electronic or physical proof of vaccination to enter certain places, including restaurants. British Columbia and Ontario are scheduled to impose similar restrictions later this month.

The Ontario government announced its vaccine passport system on Wednesday. The next day, bookings by people seeking the shots more than doubled, the provincial health minister, Christine Elliott, said on Twitter. “Today, we’re already seeing thousands more Ontarians roll up their sleeves, nearly half of whom are receiving their first dose,” she said.

Other provinces have gone in a different direction.

Alberta, which does not have a vaccine passport system, on Friday reinstated an indoor mask requirement and announced a cash incentive of 100 Canadian dollars on a prepaid debit card for people over 18 who get vaccinated by Oct. 14. The province has also awarded the second of three lottery prizes of one million Canadian dollars each to spur inoculations, and dozens of other smaller prizes. The province has the highest rate of active coronavirus cases in the country, according to national public health data.

The White House on Friday unveiled a $65.3 billion, 10-year pandemic preparedness plan that it likened to the Apollo mission to the moon. It called on Congress to immediately allocate at least $15 billion in the budget reconciliation bill for the effort — half the amount President Biden initially proposed.

The plan, drafted by Mr. Biden’s science adviser and his National Security Council, would establish a full-time “Mission Control” office that would coordinate the work of agencies across the government to spot emerging threats and ready the nation to fight them.

“We have a tremendous amount to do for this pandemic, and we really have to think about creating capabilities that may take several years to develop, but they can be truly transformative for the next event that we will see surely in the coming decades,” said Dr. Eric Lander, one of two officials who previewed the plan for reporters.

The $15 billion would be a compromise. In March, the White House announced that its American Jobs Plan would include $30 billion for pandemic preparedness. But on Capitol Hill, where moderate Democrats are pushing to lower the price tag of the $3.5 trillion budget reconciliation bill, a figure of $8 billion for pandemic preparedness has been under consideration.

Some Democrats have repeatedly called for the initial $30 billion to be included in the reconciliation package. Among them is Senator Patty Murray, Democrat of Washington and the chairwoman of the Senate Health Committee, and Senator Elizabeth Warren, Democrat of Massachusetts. Ms. Warren and six of her Democratic colleagues recently wrote to the House and Senate leaders of both parties, calling on them to include $30 billion in the budget package.

“The Covid-19 pandemic has made clear that underinvesting in our public health infrastructure, our biomedical research pipeline and our medical supply chain has disastrous consequences,” the senators wrote.

The advocacy group Guarding Against Pandemics is also calling on Congress to put $30 billion for pandemic preparedness in the budget bill. The group fears that while there was an enormous investment in fighting Covid-19, lawmakers will give short shrift to preventing future pandemics.

Dr. Lander was joined Friday by Elizabeth Cameron, the senior director for global health security and biodefense on the National Security Council — a job she held in the Obama White House, where she drafted a preparedness document known as the pandemic playbook. She said the Biden plan “very much draws on those efforts,” as well as “on lessons from this pandemic.”

According to documents released by the White House, the plan has five central goals: improving and expanding the nation’s arsenal of vaccines, therapeutics and diagnostics; improving surveillance of infectious disease threats; strengthening the public health system, with a “particular focus on reducing inequities”; building up the supply chain and the stockpile, including personal protective gear; and “managing the mission,” by creating a new Mission Control office — a task Dr. Lander likened to the Apollo mission to send astronauts to the moon in the 1960s.

“If you’re getting to the moon, and you have a great booster rocket but you haven’t got a capsule capable of landing work computers capable of directing, it’s not going to work,” he said.

Top federal health officials have told the White House to scale back a plan to offer coronavirus booster shots to the general public later this month, saying that regulators need more time to collect and review all the necessary data, according to people familiar with the discussion.

Dr. Janet Woodcock, the acting commissioner of the Food and Drug Administration, and Dr. Rochelle P. Walensky, who heads the Centers for Disease Control and Prevention, warned the White House on Thursday that their agencies may be able to determine in the coming weeks whether to recommend boosters only for recipients of the Pfizer-BioNTech vaccine — and possibly just some of them to start.

The two health leaders made their argument in a meeting with Jeffrey D. Zients, the White House pandemic coordinator. Several people who heard about the session said it was unclear how Mr. Zients responded. But he has insisted for months that the White House will always follow the advice of government scientists, wherever it leads.

Asked about the meeting, a White House spokesman on Friday said, “We always said we would follow the science, and this is all part of a process that is now underway,” adding that the administration was awaiting a “full review and approval” of booster shots by the F.D.A. as well as a recommendation from the C.D.C.

“When that approval and recommendation are made,” the spokesman, Chris Meagher, said, “we will be ready to implement the plan our nation’s top doctors developed so that we are staying ahead of this virus.”

Less than three weeks ago, Mr. Biden said that, contingent on F.D.A. approval, the government planned to start offering boosters the week of Sept. 20 to adults who had received their second shot of the Pfizer-BioNTech or Moderna vaccine at least eight months ago. That would include many health care workers and nursing home residents, as well as some people older than 65, who were generally the first to be vaccinated. Administration officials have said that recipients of the single-dose Johnson & Johnson vaccine would probably be offered an additional shot soon as well.

Britain’s vaccine watchdog declined on Friday to endorse Covid shots to all children between 12 and 15 years old, advising the government that the health benefits were only “marginally greater than the potential known harms,” and the margin was “too small to support universal Covid-19 vaccination for this age group at this time.”

However, the watchdog, the Joint Committee on Vaccination and Immunisation, suggested that officials could seek further input from the United Kingdom’s chief medical officers, who hold advisory positions similar to that of the U.S. surgeon general.

Top health officials immediately did so, a move that raises the possibility that U.K. governments could take the extraordinarily rare step of not abiding by the committee’s judgment.

Sajid Javid, Britain’s health secretary, said in a statement that he had joined with the health ministers of the four U.K. nations — England, Scotland, Wales and Northern Ireland — in writing to their chief medical officers to request assessments of the value of expanding vaccination eligibility to all 12- to 15-year-olds. Mr. Javid’s statement said the advice would be considered and that a decision would be made “shortly.”

The committee explained its caution as stemming from two factors: the very low rates of severe Covid in the young and the “extremely rare” reports of inflammation of the heart muscle after receiving mRNA vaccines — those made by Pfizer-BioNTech and Moderna — in younger adults.

The committee had already recommended vaccinations for those in the age group with health conditions like severe neurological disorders or immunosuppression that increase vulnerability to severe Covid, as well as for those living with an immunosuppressed person. On Friday, it advised broadening the list of the qualifying conditions to include conditions like heart disease, severe asthma, sickle cell disease, Type 1 diabetes, cerebral palsy, autism, epilepsy and muscular dystrophy.

That would open eligibility to 200,000 more young people, the BBC reported.

Britain was one of the countries hardest hit in the first wave of the pandemic, and suffered an enormous winter surge in which Covid deaths averaged 1,200 a day. The Delta variant drove another surge this summer, reaching a peak of 60,000 cases in mid-July. Cases fell to half that within two weeks, though they have since been climbing again.

However deaths remain relatively low at around 100 a day, a fact British officials say demonstrates the power of vaccination to break the link between infections and severe disease. Even with millions of younger people ineligible, 63 percent of the entire population is fully vaccinated.

Since the beginning of the pandemic, doctors have found that people who become very ill with Covid-19 often experience kidney problems, not just the lung impairments that are the hallmark of the illness.

Now, a large study suggests that kidney issues can last for months after patients recover from the initial infection, and may lead to a serious lifelong reduction of kidney function in some patients.

The study, published Wednesday in the Journal of the American Society of Nephrology, found that the sicker Covid patients were initially, the more likely they were to experience lingering kidney damage. But even people with less severe initial infections could be vulnerable.

“You see really, across the board, a higher risk of a bunch of important kidney-associated events,” said Dr. F. Perry Wilson, a nephrologist and associate professor of medicine at Yale, who was not involved in the study. “And what was particularly striking to me was that these persisted.”

Kidneys play a vital role in the body, clearing toxins and excess fluid from the blood, helping maintain a healthy blood pressure, and keeping a balance of electrolytes and other important substances. When the kidneys are not working properly or efficiently, fluids build up, leading to swelling, high blood pressure, weakened bones and other problems. The heart, lungs, central nervous system and immune system can become impaired. In end-stage kidney disease, dialysis or an organ transplant may become necessary. The condition can be fatal.

The new study, based on records of patients in the Department of Veterans Affairs health system, analyzed data from 89,216 people who tested positive for the coronavirus between March 1, 2020, and March 15, 2021, as well as data from 1,637,467 people who were not Covid patients.

Between one and six months after becoming infected, Covid survivors were about 35 percent more likely than non-Covid patients to have kidney damage or substantial declines in kidney function, said Dr. Ziyad Al-Aly, chief of the research and development service at the V.A. St. Louis Health Care System and senior author of the study.

Oscar De La Hoya, the aging hall of fame boxer, said he has been hospitalized with Covid-19 and he will not take part in a comeback fight planned for later this month.

Mr. De La Hoya, 48, posted videos on Instagram and Twitter on Friday of himself in a hospital bed in Los Angeles. He says in Spanish to the camera that had been diagnosed with Covid-19 even though he was fully vaccinated.

“Me siento mal, mal, mal, mal, tengo Covid, mi pecho no — no puedo respirar bien.” “I feel bad, bad, bad, bad, I have Covid, my chest doesn’t — I can’t breathe well.”

The boxer, who retired with a 39-6 professional record and won numerous world titles, hasn’t fought in a professional boxing match since he lost to Manny Pacquiao in 2008. Mr. De La Hoya had been training in recent months for an match against Vitor Belfort, a former UFC champion, on Sept. 11 at the Staples Center in Los Angeles.

In recent years, Mr. De La Hoya, whose nickname was “Golden Boy,” has worked as a boxing promoter and last year helped push to bring boxing back during the pandemic, even if it meant there would be no fans in the arena. He will be replaced in the fight by Evander Holyfield, ESPN reported.

SEOUL — Five of the seven members of the South Korean boy band Enhypen have tested positive for the coronavirus. For the group’s fans, and potentially others in South Korea, the infections put a public face on the urgency behind a vaccination drive in a country that has been slow to acquire shots and began administering them to all adults only last week.

The announcement on Thursday by the group’s label, Belift Lab, comes at a time when South Korea is on high alert. Restrictions have been raised to the highest level in Seoul for months. Infections have reached more than 1,400 a day on average, according to a Times database, a low level compared with many other countries but well above the rate the authorities had recorded months before.

The country remains vulnerable. Only about 31 percent of the country’s population has been fully vaccinated, according to the Our World in Data project at the University of Oxford. South Korea was later than other countries to order vaccines, leaving its supplies short.

So far, the demand for shots is high. About 83 percent of people ages 18 to 49 have booked or received a vaccine, the health authorities said on Friday.

After Enhypen’s announcement, thousands of fans on social media said they feared that the group would delay the release of its third album. It canceled the performance it was scheduled to give later this month at KCON, an annual Korean culture and music convention.

Many fans urged others to get their shots. “Get well soon, Enhypen,” one wrote, “and everyone please wear your masks and get vaccinated.”

Since its November debut on a K-pop reality TV show called “I-Land,” Enhypen has accumulated 3.9 million subscribers on YouTube and 4.6 million monthly listeners on Spotify. It is one of the most popular active K-pop groups, ranking among others like BTS and Blackpink.

Enhypen’s second and most recent album, “Border:Carnival,” sold more than half a million copies in less than a week after its release in April, ranking first on the country’s album chart.

All seven members of Enhypen had entered quarantine the day after a member of the production crew tested positive on Aug. 25, the label said. Five of them — Jake, Jungwon, Heeseung, Jay and Sunghoon — began to suffer from coughs and fevers, and subsequently tested positive.

“We apologize for causing concern to all fans,” the label said, and for “being unable to prevent the occurrence of this series of infections despite our effort to ensure that precautions were in place.”

All of the artists and staff in quarantine are being tested twice a day and closely monitored, according to the label.

Over the past week, an average of roughly 163,600 coronavirus cases has been reported each day in the United States, an increase of 12 percent from two weeks ago. Total cases are likely to surpass 40 million within days.

Oregon, Kentucky and Guam have reported more coronavirus cases in the past week than in any other seven-day period. Florida has reported more coronavirus deaths in the past week than in any other seven-day period.

More than 101,500 coronavirus patients are hospitalized nationwide, including more than 15,500 in Florida, which has a far higher hospitalization rate than any other state.

Kentucky is also near its worst point ever, having reached an all-time high in its daily case average on Monday.

The nation’s daily reports of of new deaths are up 59 percent, to an average of 1,550 deaths per day.

That is nearly half the country’s highest average of 3,352, reached on Jan. 12.

Weekly Covid deaths in Florida have been breaking state records since Aug. 19 and again hit a new high of 2,277 for the past week.

The pace of vaccinations continues to increase as more workplaces require employees to get the shots. Around 900,000 doses are being administered each day, up from a low of 506,771 on July 11. However, the current average is 73 percent lower than the peak average of 3.38 million reached in mid-April.

About 62 percent of the eligible American population (age 12 and over) are fully vaccinated and another 11 percent have received the first dose of a two-dose vaccine.

Ten states have fully vaccinated more than 70 percent of their adult populations, with the highest level of 78 percent reached by Vermont. The others are Massachusetts, Connecticut, New Mexico, New Jersey, Rhode Island, Maine, Washington, Maryland and New York. Two U.S. territories, Puerto Rico and Guam, have also passed 70 percent.

Four states have not yet fully vaccinated 50 percent of their adult populations: Alabama, Mississippi, Wyoming and West Virginia.

A close military aide to Iran’s supreme leader who led the armed forces for 27 years and once accused Western enemies of deploying lizards to spy on Iranian nuclear activities has died from Covid-19.

The death of Maj. Gen. Hassan Firouzabadi, 70, was reported Friday by Iranian news outlets as the country grapples with its fifth wave of coronavirus infections — and as Iranians have grown increasingly irate at the government’s response.

The Delta variant has overwhelmed Iran’s hospitals, and last month the country reported record daily deaths and infections. Only 10 percent of the population has been fully vaccinated, according to a New York Times database.

General Firouzabadi was an ophthalmologist by training. Under Iran’s supreme leader, Ayatollah Ali Khamenei, he served as the chief of staff of the armed forces from 1989 to 2016, when he was succeeded by his deputy, Maj. Gen. Mohammad Hossein Bagheri. General Firouzabadi, who was said to have struggled with obesity, went on to serve as an adviser to Mr. Khamenei.

General Firouzabadi was often quoted in Iranian news media, boasting of Iran’s military might and warning its enemies, mainly Israel and the United States, against posing any challenges.

He is remembered abroad in part for an accusation he made against Western intelligence in 2018, after Iranian security officials had arrested environmentalists and suggested they were spies. General Firouzabadi said enemy surveillance agents had been known to plant desert reptiles and chameleons in Iran to detect nuclear work.

“We found out their skin attracts atomic waves and that they were nuclear spies who wanted to find out where inside the Islamic republic of Iran we have uranium mines, and where we are engaged in atomic activities,” he was quoted as having told reporters.

Since November 2020, Kerry Kijewski has been waiting to connect in person with a man she met online during the winter lockdown in Ontario, Canada. Despite the fact that he lives only 40 minutes from her London home, their dating relationship has been entirely virtual.

Ms. Kijewski, 37, who is at high risk of complications should she contract Covid-19 because of a kidney transplant, was fully vaccinated by May. Her prospective love interest recently received his second dose, but with the Delta variant surging, she is unsure whether it’s safe to meet in person.

“I feel the pressure to meet soon before things worsen again, but I am afraid to do many things out of my house these days,” she said. “The fear is real, but I don’t want it to take over.”

During the world’s collective stretch of virtual living, daters like Ms. Kijewski pledged to hit the singles scene with a vengeance once fully vaccinated against Covid. Yet as the proposed “hot vax summer” comes to a close, many daters are retaining some of the more cautious behaviors that the pandemic has necessitated.

While not much hard data exists yet on the coronavirus’s effect on dating, surveys suggest plenty of people are taking re-entry into the dating field more slowly than previously expected.

“While a sexy ‘hot vax summer’ sounded great when cases were dropping, the latest news on the pandemic suggests people will still be very focused on health and safety for the foreseeable future, and that goes for new relationships, too,” said Liz Meyerdirk, chief executive of the Pill Club, a telehealth company that provides contraceptives among other products.

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E.U. Ends Legal Battle With AstraZeneca

The European Union reached a settlement with the company over delays in the delivery of hundreds of millions of Covid-19 vaccine doses. The agreement requires AstraZeneca to deliver a total of 300 million doses by the end of March 2022.

Today, the European Commission and AstraZeneca have reached a settlement agreement, which will put an end to the pending litigation cases before the Brussels court. The settlement agreement secures the delivery of the remaining Covid-19 vaccine doses to member states due under the advance purchase agreement. Under this settlement agreement, AstraZeneca has the firm commitment to deliver — in addition to the 100 million doses, which have been delivered by the end of the second quarter of this year — another 135 million doses in 2021, and 65 million doses by end of March 2022.

The European Union reached an agreement with AstraZeneca in a legal battle over delays in the company’s delivery of hundreds of millions of Covid-19 vaccine doses, ending a longstanding dispute.

The settlement, which obliges AstraZeneca to deliver a total of 300 million doses by the end of March 2022, will end all pending legal proceedings, the European Commission, the bloc’s administrative arm, said in a statement. So far, the company has delivered 140 million doses to the bloc’s member nations.

AstraZeneca will provide E.U. countries with regular delivery schedules. If there are delays in the delivery of the doses, the countries will get rebates.

The vaccine developed by the Anglo-Swedish company and Oxford University was the initial pillar of the E.U. vaccination strategy. The conflict began when AstraZeneca substantially cut its expected deliveries for the first quarter of 2021, as coronavirus cases were picking up across the continent. This was a major blow to the bloc’s vaccine rollout, contributing to its sluggish start. E.U. officials accused AstraZeneca of giving the promised doses to Britain, which had just left the bloc at the time.

In an abrupt escalation, the European Union sued AstraZeneca in April over the delivery delays, asking a court in Brussels to compel the company to supply a total of 300 million doses by September. It proposed penalties including 10 million euros a day (about $11.9 million) for each of four alleged breaches of contract, an amount which could have rapidly ballooned into the billions.

In a ruling in June, a court in Brussels said that AstraZeneca had to deliver 50 million additional doses by late September, which was hundreds of millions fewer than the bloc demanded. More legal proceedings were expected later this month.

But as the E.U. inoculation rollout gained speed, with 70 percent of the bloc’s adults now fully vaccinated, the battle over undelivered doses lost its urgency. Although big discrepancies remain in vaccination rates among member nations, with poorer, eastern countries lagging behind, the challenge is not the supply of vaccine doses but their administration, which is a prerogative of national governments.

Stella Kyriakides, the bloc’s health commissioner, said in a statement that “the continued availability of vaccines, including AstraZeneca, remains crucial,” adding that the European Union had committed to donating at least 200 million doses to low- and middle-income countries outside the bloc by the end of the year.

“Vaccine solidarity is and remains our trademark,” Ms. Kyriakides added.

In India and Indonesia, in Mexico and Israel, in Britain and in France, students headed back to school this week — with some returning to classrooms for the first time in more than a year.

Despite the fast-spreading Delta variant of the coronavirus, many students returned to traditional in-person learning. Some were masked. Others were able to show off gaptoothed grins after losing baby teeth over the summer break.

This week, the World Health Organization urged countries to do whatever they could to keep children in schools.

“We encourage all countries to keep schools open and urge all schools to put in place measures to minimize the risk of Covid-19 and the spread of different variants,” the World Health Organization’s director for Europe, Hans Kluge, said in a statement released jointly with the United Nations children’s agency, UNICEF.

In many countries, officials are doing just that.

India’s capital, New Delhi, reopened schools on Wednesday after five months of closures. New infections have fallen, and officials have argued that reopening schools was crucial for children’s physical and mental health. Classes resumed for students in grades 9 to 12, with some restrictions: no crowding, no sharing of food or drinks, no guest lectures. Schools in the neighboring state of Uttar Pradesh, which had reopened for students in grades 6 to 12 last month, allowed primary school classes to open on Wednesday.

More than 11 million students in Mexico returned to in-person classes, the authorities said, after nearly a year and a half out of school. Last month, the country’s education ministry issued a 10-point plan to reduce the risk of infection, including checking students’ temperatures when they arrive and making sure they wear masks. Teachers will need to do the same, the ministry said. The authorities are also encouraging schools use outdoor spaces and avoid large gatherings or ceremonies.

Mexico’s vaccine rollout has been agonizingly slow, and more than 100,000 children aged 14 and under have been infected with Covid-19, official figures show.

Schools in Jakarta, Indonesia, have reopened after being closed since March 16, 2020. Classes will be limited to half their usual size, and in-person schooling will be mixed with distance learning. In-person learning will slowly increase as the government monitors the situation, over a transition period scheduled to last two months.

After 18 months of intermittent disruptions, students are set to return to schools and colleges across Britain over the next few weeks, with the authorities keeping some protective measures in place to avoid outbreaks. These include testing in high schools and colleges as well as regular testing at home, improved ventilation and extra hygiene efforts. “I have every confidence that school and college staff, parents and students will continue to work together admirably, following pragmatic measures like testing and vaccinations to minimize disruption and keep children where they belong — in the classroom,” Gavin Williamson, the country’s education secretary, said last week.

Israel reopened its schools on Wednesday in a festive atmosphere even as it grappled with a surge in Delta infections and a rate of new daily cases that is among the highest in the world.

Sobered by a too-hasty back-to-school policy last year, which led to new outbreaks and, eventually, another lockdown, the Ministry of Education introduced a series of measures aimed at keeping as many classes open as possible while minimizing the risk of spreading the virus. Anybody entering a school or kindergarten has to present proof of vaccination or a negative test, and families were given free rapid tests before the opening.

Students in higher grades who live in areas with high infection rates will learn outdoors or remotely if less than 70 percent of their class is vaccinated or has recovered from Covid-19.

French children, who returned to school on Thursday, are required to be masked in classrooms and are expected to distance themselves and wash their hands frequently. Primary schools will close for a week if a student is found to be infected. In secondary and high schools, unvaccinated students who were in contact with someone who tested positive will be required to attend school remotely for a week, while fully vaccinated students can stay in class as normal.

Léontine Gallois, Aina J. Khan, Isabel Kershner, Oscar Lopez, Karan Deep Singh and Muktita Suhartono contributed reporting.

About a fifth of Kentucky’s school districts have had to temporarily close since classes began last month because of coronavirus infections, an indication of the dire impact the most recent wave of the virus has had on the state.

Kentucky has recently reached its highest levels of cases and hospitalizations since the start of the pandemic, largely because of the highly infectious Delta variant. Hospitals are becoming overwhelmed, and Gov. Andy Beshear said on Thursday he was deploying the National Guard to help medical professionals.

The rise in cases has also affected Kentucky’s schoolchildren, hundreds of thousands of whom are under 12 and so not eligible for vaccination. “More kids are getting Covid right now than we ever thought imaginable,” Mr. Beshear said at a news conference on Monday.

As of Friday, 34 of the state’s 171 school districts had closed at some point during the new school year because of infections and quarantines, said Josh Shoulta, a spokesman for the Kentucky School Boards Association.

The Centers for Disease Control and Prevention has emphasized returning to in-person classes, ideally with as many people as possible vaccinated and measures like universal masking in place. But those measures have become politically fraught. On Friday, anti-mask protesters demonstrating against Washington State’s mask mandate in schools forced several to close in the southern city of Vancouver (named for the same 18th century British sea captain as the younger but much larger city in Canada).

Many states are in the midst of their worst wave of the pandemic since last winter, and children are very much a part of it. According to data collected by the American Academy of Pediatrics the number of cases in children increased exponentially, up from about 38,000 cases the week ending July 22 to nearly 204,000 for the last full week in August. Pediatric Covid hospitalizations are soaring.

In August, Mr. Beshear, a Democrat, rescinded an executive order mandating masks in schools after the state Supreme Court upheld laws passed by the Republican-led state Legislature limiting his power. However, Kentucky’s Department of Education has a mask requirement in place for public schools, in line with federal recommendations intended to make the resumption of in-person schooling as safe as possible.

Toni Konz Tatman, an Education Department spokesman, said that the mask rule appeared to make a difference based on the experience of some districts. “We had a couple districts that opened before the regulation was passed and their number of quarantines was significantly higher,” she said.

Reopening schools has also been complicated by a shortage of personnel, especially substitute teachers and bus drivers, that was greatly worsened by rampant coronavirus infections and quarantines, Ms. Tatman said.

“Our districts are pulling in all the people they can, they really are exhausting every possibility they can, but when it gets to the point where they can’t pull it off they are closing,” she said.

For now, the hope of normalcy that many educators and parents had entertained has not come to pass, she said.

“I think a lot of people were hopeful that we could start the year differently,” Ms. Tatman said. “It’s just not the case.”