Medical experts welcomed the news that the Pfizer-BioNTech Covid vaccine could be authorized by the Food and Drug Administration for use in adolescents ages 12 to 15 by early next week, a major step forward in the U.S. vaccination campaign.

Vaccinating children is key to raising the level of immunity in the population, experts say, and to bringing down the numbers of hospitalizations and deaths. And it could put school administrators, teachers and parents at ease if millions of adolescent students soon become eligible for vaccinations before the next academic year begins in September.

Pfizer’s trial in adolescents showed that its vaccine was at least as effective in them as it was in adults. The F.D.A. is preparing to add an amendment covering that age group to the vaccine’s existing emergency use authorization by early next week, according to federal officials familiar with the agency’s plans who were not authorized to speak publicly.

Dr. Ashish K. Jha, dean of the Brown University School of Public Health and the father of two adolescent daughters, said the approval would be a big moment for families like his.

“It just ends all concerns about being able to have a pretty normal fall for high schoolers,” he said. “It’s great for them, it’s great for schools, for families who have kids in this age range.”

But with demand for vaccines falling among adult Americans — and much of the world clamoring for the surplus of American-made vaccines — some experts said the United States should donate excess shots to India and other countries that have had severe outbreaks.

“From an ethical perspective, we should not be prioritizing people like them over people in countries like India,” Dr. Rupali J. Limaye, a Johns Hopkins University researcher who studies vaccine use, said of adolescents.

Dr. Jha said that the United States now had a big enough vaccine supply to both inoculate younger Americans and aid the rest of the world. As of Monday, the United States had about 65 million doses delivered but not administered, including 31 million doses of the Pfizer-BioNTech vaccine, according to figures collected by the Centers for Disease Control and Prevention.

More than 105 million adults in the United States have been fully vaccinated. But the United States is in the middle of a delicate and complex push to reach the 44 percent of adults who have not yet received even one shot.

While adolescents so far appear to be mostly spared from severe Covid-19, Dr. Anthony S. Fauci, the Biden administration’s top Covid adviser, has repeatedly stressed the importance of expanding vaccination efforts to include them and even younger children. In March, Dr. Fauci said that he expected that high schoolers could be vaccinated by fall and elementary school students by early 2022.

Dr. Richard Malley, a pediatric infectious disease specialist at Boston Children’s Hospital, said that immunizing adolescents was worthwhile because they can spread the virus, even if they transmit it at a lower rate than adults.

Even in China, where propaganda has become increasingly pugnacious, the display was jarring: A photograph of a Chinese rocket poised to blast into space juxtaposed with a cremation pyre in India, which has been overwhelmed by a wave of coronavirus infections.

“Chinese ignition versus Indian ignition,” the title read.

The image drew a backlash from internet users who called it callous, and it was taken down on the same day by the Communist Party-run news service that posted it. But it has lingered as a provocative example of a broader theme running through China’s state-run media, which often celebrates the country’s success in curbing coronavirus infections while highlighting the failings of others.

Chinese leaders have expressed sympathy and offered medical help to India, and the controversy may soon pass. But it has exposed how swaggering Chinese propaganda can collide with Beijing’s efforts to make friends abroad.

“You’ve had this growing tension between internal and external messaging,” said Mareike Ohlberg, a senior fellow in the Asia Program at the German Marshall Fund in Berlin who studies Chinese propaganda. Ms. Ohlberg said of the Chinese authorities, “They have an increasing number of interests internationally, but ultimately what it boils down to is that your primary target audience still lives at home.”

Savita Mullapudi, an international development consultant in Pittsburgh, heard the ping of a WhatsApp message on her phone around 4 p.m. on Thursday. The sender was a former colleague who, like her, was an Indian immigrant who had lived in the United States for years. He had an urgent favor to ask.

With India’s health care system overwhelmed by the nation’s unprecedented Covid-19 surge and hospitals running out of lifesaving oxygen, an Indian charity was scrambling to find oxygen concentrators, which filter oxygen from the air. One manufacturer was based in Pittsburgh. Could Ms. Mullapudi visit the site to vet the equipment?

Like many members of the Indian diaspora who have watched and mobilized from afar as a deadly second wave of the coronavirus has swept across India in recent weeks, Ms. Mullapudi, whose parents and in-laws live there, leapt at the opportunity to help. She called the company a few minutes later but was told the earliest date for a visit was May 8 — far too late.

So Ms. Mullapudi, 44, said she did “the next-best thing.” She asked a few local doctor friends to tap their networks in Pittsburgh and across Pennsylvania for their opinions of the company and the quality of its products.

By 9 a.m. the next day, she had received texts and long emails from medical professionals and hospital executives with “rave reviews” of the manufacturer, she recalled, as well as detailed descriptions of the machines’ electricity costs and how long they lasted.

“The minute I said ‘India Covid,’ I was inundated with responses,” Ms. Mullapudi said. “These networks of people that we all work with or know as friends just churned it around, and that’s what really gave the organization confidence to go ahead.”

Before noon on Friday, the foundation ordered more than 400 oxygen concentrators to be flown to India. Though Ms. Mullapudi described her role as just “one drop in an ocean,” she acknowledged the profound impact of so many small acts of human kindness in the face of such dire challenges.

“Eventually it’s just people helping people,” she said. “That’s the story of hope.”

On Tuesday, Pfizer announced that its Covid vaccine brought in $3.5 billion in revenue in the first three months of this year, nearly a quarter of its total revenue. The vaccine was, far and away, Pfizer’s biggest source of revenue, report Rebecca Robbins and Peter S. Goodman of The New York Times.

The company did not disclose the profits it derived from the vaccine, but it reiterated its previous prediction that its profit margins on the vaccine would be in the high 20 percent range. That would translate into roughly $900 million in pretax vaccine profits in the first quarter.

Pfizer has been widely credited with developing an unproven technology that has saved an untold number of lives.

But the company’s vaccine is disproportionately reaching the world’s rich — an outcome, so far at least, at odds with its chief executive’s pledge to ensure that poorer countries “have the same access as the rest of the world” to a vaccine that is highly effective at preventing Covid-19.

As of mid-April, wealthy countries had secured more than 87 percent of the more than 700 million doses of Covid-19 vaccines dispensed worldwide, while poor countries had received only 0.2 percent, according to the World Health Organization. In wealthy countries, roughly one in four people has received a vaccine. In poor countries, the figure is one in 500.

The Hong Kong government on Tuesday backpedaled from a plan to require coronavirus vaccinations for all foreign domestic workers after several days of sharp criticism from foreign diplomatic missions and some residents, who called the requirement discriminatory.

Officials had announced on Friday that the domestic workers — largely low-paid, female migrants from Southeast Asia who clean, cook and perform other household tasks — would have to be vaccinated in order to renew their employment contracts. The government has not issued vaccination requirements for any other group in the city, including other foreign workers.

But officials said it was necessary after two domestic workers recently tested positive for variant strains of the coronavirus. Sophia Chan, the secretary for food and health, said that because domestic workers had a habit of “mingling” with each other during their time off — which, under Hong Kong law, is only one day a week — the entire group of roughly 370,000 workers was considered high-risk.

Hong Kong’s vaccine uptake has been slow, and none of its major outbreaks of the coronavirus have been attributed to domestic workers gathering on their days off.

The announcement provoked an immediate backlash, with critics alleging that the government was making scapegoats of the domestic workers, who make up about 5 percent of Hong Kong’s population of 7.5 million and have long endured poor treatment.

The consuls general of the Philippines and Indonesia — the two main sources of Hong Kong’s foreign domestic workers — said that if there were vaccination requirements, they should be applied to all foreign workers. The Philippines’ outspoken foreign secretary tweeted that the move “smacks of discrimination.”

The government denied that it was discriminating against the workers, but on Tuesday, Carrie Lam, the city’s chief executive, said that in light of the “discussion and attention” that the plan had elicited, she would ask the labor department to “study the specific situation again” and consult foreign consulates. A decision on the plan would be announced later, she said.

Still, the government has said that all foreign domestic workers who have not been fully vaccinated must be tested for the coronavirus by May 9.

These days, visitors to the website of one of Italy’s most renowned contemporary art museums are met with a twofold invitation: “Book your visit in advance” and “Book your vaccination.”

The Castello di Rivoli, once a palace owned by the Savoy dynasty, recently became one of several Italian museums to join the country’s vaccine drive, following in the footsteps of cultural institutions throughout Europe.

With the rallying cry of “Art Helps,” the museum near Turin has set aside its third-floor galleries for a vaccination center run by the local health authorities. During their shots, patients can enjoy the wall paintings by Claudia Comte, a Swiss artist.

Comte worked with the composer Egon Elliut to create a soundscape that evokes “a dreamlike feeling,” the artist said, and lulls vaccine recipients as they move from room to room before and after the shot.

“Art has an extraordinarily important effect on well-being,” said Carolyn Christov-Bakargiev, the museum’s director. She said that she couldn’t have commissioned “a more perfect” backdrop than Comte’s works for a “space to merge the art of healing the body and the art of healing the soul and the mind,” noting that in Italian the words for “to heal” and “curator” came from the same Latin word, “curo.” In history, she said, some of the first museums were former hospitals.

Less than two months after Tanzania’s first female president took office, the government on Monday announced new steps to tackle the pandemic, a significant shift for the East African nation whose late former leader had denied the seriousness of the virus.

Beginning Tuesday, all travelers arriving in Tanzania are required to present proof of a negative coronavirus test taken in the previous 72 hours and must pay for a rapid test after they land, the health ministry said.

The ministry said that foreigners arriving from countries with new Covid-19 variants would be placed in a mandatory 14-day quarantine at a government-designated facility, while returning residents would be permitted to isolate themselves in their homes. The announcement did not specify which countries these measures would apply to.

Truck drivers crossing borders will be permitted to stop only at designated locations and could be tested for the coronavirus at random while in Tanzania.

“Based on the global epidemiological situation and emergence of new variants of viruses that cause Covid-19, there is an increased risk of their importation,” Abel N. Makubi, the permanent secretary of health, said in a statement. As such, he added, the government “decided to elevate and enhance prevailing preventive measures especially those with regard to international travel.”

The new measures under President Samia Suluhu Hassan represent a departure from the blithe approach taken by Tanzania’s former president, John Magufuli, who died in March. Mr. Magufuli long opposed masks and social distancing measures, promoted unproven treatments as cures, argued that vaccines didn’t work and declared that God had helped Tanzania eradicate the virus.

His government also stopped sharing coronavirus data with the World Health Organization. Tanzania has recorded no new cases of the virus since April last year, when it reported 509 infections and 21 deaths.

Two weeks before he died, Mr. Magufuli changed course and told citizens to take precautions against the virus, including wearing masks and observing social distancing.

But since her ascension to power, Ms. Hassan has taken a different turn, stating that Tanzania could not ignore the virus. In early April, she said she would set up a committee to investigate the pandemic and advise the government on its response.

“We cannot isolate ourselves as an island,” Ms. Hassan said in a speech last month.

But Ms. Hassan has also drawn criticism at times for not wearing a mask, including at her own swearing-in ceremony, and for addressing large gatherings of unmasked supporters.

Greece has reopened to many overseas visitors, including from the United States, jumping ahead of most of its European neighbors in restarting tourism,even as the country’s hospitals remain full and more than three-quarters of Greeks are still unvaccinated.

It’s a big bet, but given the importance of tourism to the Greek economy — the sector accounts for one quarter of the country’s work force and more than 20 percent of gross domestic product — the country’s leaders are eager to roll out the welcome mat.

In doing so, Greece has jumped ahead of other European countries. On Monday, the European Commission, the executive arm of the European Union, said it would recommend its member states to allow visitors who have been vaccinated. But it remains up to individual countries to set up their own rules.

“We welcome a common position” on restarting tourism in the European Union, Greece’s tourism minister, Harry Theoharis, said in an interview. “All we’re saying is that this has to be forthcoming now. We cannot wait until June.”

At a moment when the pandemic has unleashed demand for open space, plans could transform the medians of Park Avenue in Manhattan and restore them to their original splendor.

Among the options New York City is considering: bringing back chairs and benches, expanding the median, eliminating traffic lanes and carving out room for bike and walking paths.

The revamping of Park Avenue is being driven by a major transit project below ground. A cavernous shed used by Metro-North commuter trains that travel in and out of Grand Central Terminal is over a century old and in need of major repairs.

The work requires ripping up nearly a dozen streets along Park Avenue, from East 46th to East 57th Streets, making possible a new vision.

Removal of traffic lanes is likely to elicit backlash from drivers who complain that pedestrian plazas and bike lanes across the city have made it difficult to get around.

But others say the city would be more livable with fewer cars, making streets safer for pedestrians and bicyclists as well as polluting less.