Countries across the Asia-Pacific region are scrambling to slow the spread of the more infectious Delta variant, reimposing restrictions and stay-at-home orders in a jarring reminder — for societies that had just begun to reopen — that the pandemic is far from over.

In Australia, outbreaks of the variant have forced four major cities — Sydney, Brisbane, Perth and Darwin — into strict lockdowns. On Monday, the Malaysian government said nationwide stay-at-home orders would be extended indefinitely. And Hong Kong officials banned flights from Britain, where cases of the Delta variant, which was first identified in India, are rising fast.

In Bangladesh, soldiers are preparing to patrol the streets to enforce stay-at-home orders, with new cases rapidly approaching their early April peak. “The Delta variant of Covid-19 is dominating,” said Robed Amin, a health ministry spokesman, adding that testing suggested the strain was responsible for more than 60 percent of new cases.

The lockdowns and restrictions have deflated hopes across the region, where many countries avoided the worst of the pandemic’s initial spread last year. Now, weary residents are frustrated by what some describe as their countries’ pandemic regression, as other parts of the world edge toward normalcy.

Outside Kuala Lumpur, Malaysia’s largest city, a restaurant owner, Marcus Low, bemoaned the fourth lockdown of the pandemic. Daily infections in Malaysia peaked in early June, but even after weeks of lockdown, new cases have dipped by only 5 percent over the past two weeks, according to New York Times data. Only 6 percent of the country’s 33 million people are fully vaccinated.

“My restaurant is known for its hospitality and shared dishes, the antithesis of social distancing,” Mr. Low said. For his and other small businesses struggling to survive, this lockdown “might be the last straw,” he said.

Others blamed slow vaccination drives for a return to restrictions.

“If we were able to get a really high vaccination rate, that changes the game completely,” said Hassan Vally, an associate professor in epidemiology at La Trobe University in Melbourne. With less than 5 percent of Australia’s population fully vaccinated, he said, “in some ways, where we’re at now is no surprise.”

The Delta strain is one of several “variants of concern” identified by the World Health Organization and the U.S. Centers for Disease Control and Prevention. Though estimates of its infectiousness differ, the variant could be 50 percent more contagious than the already faster-spreading Alpha variant, which emerged in Britain last year, health officials say.

Studies have shown that Covid-19 vaccines are still largely effective against the Delta variant, though protection is significantly lower for those who are partially vaccinated. But the experiences of several countries show that the Delta variant can spread rapidly through the unvaccinated, including children.

“Anywhere you carry out vaccination, the disease will be pushed into the unvaccinated population,” said Raina MacIntyre, a professor of global biosecurity at the University of New South Wales in Sydney.

Countries that have vaccinated relatively high percentages of their populations are moving ahead with reopening plans. In Britain, where the Delta variant now accounts for almost all new cases, officials say they still plan to lift most remaining pandemic restrictions on July 19. New cases there have more than doubled in the past two weeks, but officials believe that the country remains well protected, with nearly half the population fully vaccinated.

“While cases are now ticking up, the number of deaths remains mercifully low,” the country’s health secretary, Sajid Javid, said on Monday

Experts say that as long as the virus continues to circulate, it can acquire mutations that may present new challenges. In India, where a devastating second wave this spring caused thousands of deaths daily, Maharashtra state has reimposed partial stay-at-home orders in response to the emergence of what has become known locally as “Delta Plus,” described by scientists as a sub-lineage of the Delta variant.

Indian health officials have expressed concern that Delta Plus could spread even more easily. “There is the possibility of the third wave,” said Maharashtra’s chief minister, Uddhav Balasaheb Thackeray.

World Health Organization officials, concerned about the Delta variant, have urged even fully vaccinated people to continue wearing masks and taking other precautions.

The Centers for Disease Control and Prevention, on the other hand, told fully vaccinated Americans in May that they no longer needed to wear masks indoors or to stay six feet from other people. The agency also eased advice about testing and quarantine after suspected exposure.

Asked on Monday about the W.H.O.’s cautions, a C.D.C. spokesman pointed to the existing guidance and gave no indication it would change.

The Delta variant, a highly infectious form of the virus that has spread to at least 85 countries since it was first identified in India, is now responsible for one in every five Covid-19 cases across the United States. Its prevalence here has doubled in the past two weeks, and Dr. Anthony Fauci, the nation’s top infectious disease doctor, has called it “the greatest threat” to eliminating the virus in the United States.

Los Angeles County said on Monday that it strongly recommended that everyone wear masks indoors as a precaution against the Delta variant, adding that it accounted for nearly half of all cases sequenced in the county.

“Until we better understand how and to who the Delta variant is spreading, everyone should focus on maximum protection with minimum interruption to routine as all businesses operate without other restrictions,” county officials said in a statement.

The rise of new variants “makes it even more urgent that we use all the tools at our disposal,” Dr. Tedros Adhanom Ghebreyesus, the director-general of the W.H.O., said at a news briefing on Friday.

Though fully vaccinated people are largely protected, studies suggest the Pfizer vaccine’s efficacy against the Delta variant is slightly lower than against other variants, and significantly lower for individuals who have received only one dose.

Britain — where some two-thirds of the population have received at least one dose of the Pfizer or AstraZeneca vaccine and just under half have received two — has seen a sharp rise in cases driven by the variant. And Israel, with one of the highest vaccination rates in the world, has partially reimposed mask mandates in response to an uptick in cases.

Given how fast-moving the variant is, “the vaccine approach is not enough,” said Eric Feigl-Ding, senior fellow at the Federation of American Scientists in Washington. “We’re not at the level of vaccinations where we can release the brakes on everything else.”

Other scientists disagreed, saying guidance has to be tailored to local conditions.

“The W.H.O. is looking at a world that is largely unvaccinated, so this makes sense,” said Dr. Ashish Jha, the dean of the Brown University School of Public Health, adding that parts of the United States might also need different advice.

“If I were living in Missouri or Wyoming or Mississippi, places with low vaccination rates,” he said, “I would not be excited about going indoors without wearing a mask — even though I’m vaccinated.”

In a city whose cultural soul had been closed for more than a year, with boarded-up windows and empty streets, Bruce Springsteen called it back to life on Saturday night. His gruff and guttural rasp was the first to echo across a Broadway stage to a paying audience in 471 days.

Of course, “Springsteen on Broadway” is no traditional Broadway production. The show consists of a man alone onstage. His ensemble: a microphone, a harmonica, a piano and six steel strings stretched across a select slab of spruce wood.

“I am here tonight to provide proof of life,” Springsteen called out early on. It was a line from the monologue of his original show — which ran for 236 performances, in 2017 and 2018 — and now it carried extra weight. That proof, he continued, was “to that ever elusive, never completely believable, particularly these days, us.”

For the “us” that packed inside the St. James Theater — 1,721 filled seats, very few masked people, all vaccinated — that first chord from “Growin’ Up” was indeed proof that the rhythms that moved New York City were emerging from behind a heavy, dark and weighty curtain.

The 15 months that Broadway had been closed were its longest silence in history. In years past, strikes, hurricanes, blizzards and blackouts had managed to tamp down the lights on Broadway only for a few days, weeks or a month.

But the pandemic forced the Theater District into an extensive darkness on March 12 of last year, as New York became the epicenter of the epidemic in the United States.

The cure for high prices is high prices.

That’s an old line used in commodity markets, and it helps explain why the great inflation scare of 2021 has eased some in recent weeks. When the price of something soars because demand outstrips supply, it has a way of self-correcting. Buyers, scared off by high prices, find other options, and sellers crank up production to take advantage of a profit opportunity.

It is an idea simple enough to be taught in the first few weeks of any introductory economics class, but one with powerful implications for the American economy as it aims for a postpandemic reboot.

Several of the key products whose prices soared in the spring have grown less expensive, as producers have increased output and buyers have held tight. This is particularly evident with lumber; as of Friday, its price was down 47 percent from its early-May peak (though still well above historical norms). Sawmills responded to soaring prices by pushing the limits of their capacity.

The prices of corn, copper and a variety of other economically important commodities are also down by double-digit percentages since early May. This supports the notion that the inflation the world has been experiencing is transitory — set to ease in the months ahead as the laws of supply and demand take hold.

Markets have plenty of flaws and imperfections, but when it comes to allocating scarce goods and sending signals to sellers to make more and buyers to buy less, they work quite well.

But just because markets work doesn’t mean they will work instantly. The complexity of the way many of the goods still in short supply are produced, transported and sold means that people in those markets are reluctant to predict the kind of snapback evident in lumber prices.

Got the sniffles? Worried about that night out in a crowded club? Or maybe you just want to visit grandma but are concerned about her risk, even though you’re vaccinated.

At-home rapid Covid-19 tests, which give results in minutes, can be useful and reassuring for both the vaccinated and unvaccinated.

Given the availability of vaccines for all people 12 and older in the United States, it may be hard to imagine why anyone would still need a home test. But the coronavirus isn’t going away anytime soon, and a rise in infections this fall among the unvaccinated appears inevitable.

In most cases, regular home testing isn’t necessary for someone who is fully vaccinated. The vaccines available in the United States have been shown to be effective against the variants, including Delta. But breakthrough infections, although rare, continue to occur.

A home test can offer reassurance to a vaccinated person who has traveled recently or spent time in a crowded bar. It can be used more frequently for families with young children who aren’t yet eligible for vaccination.

Here are some scenarios in which a rapid home test may be useful:

• For unvaccinated children, who could be tested periodically before going to camp or school or right before a birthday party.

• To regularly check and protect the health of a babysitter who spends time with your unvaccinated children, or a home-health aide who is caring for a high-risk individual.

• As an added precaution for a vaccinated person who wants to spend time with a grandparent or someone who is immune compromised. (An unvaccinated person shouldn’t spend time indoors with a person at high risk.)

• To be sure a cough or sniffle is just allergies or a common cold rather than Covid-19.

• To test houseguests before a dinner party or overnight stay, if someone in the group is unvaccinated or at high risk.

• For guests at weddings or other large gatherings if they can’t provide proof of vaccination.