LONDON — Over Memorial Day weekend, 135,000 people jammed the oval at the Indianapolis 500. Restaurants across the United States were thronged with customers as mask mandates were being discarded.
The formula, which gained the Biden administration’s blessing, was succinct: In essence, if you are fully vaccinated, you can do as you please.
But while the United States appears to be trying to close the curtain on the pandemic, across the ocean, in Britain and the European Union, it is quite a different story.
Despite plunging infection levels and a surging vaccine program, parts of Europe are maintaining limits on gatherings, reimposing curbs on travel and weighing local lockdowns.
Wellcome Sanger Institute, said of Delta. “It just means we have less certainty about what things will look like going forward.”
estimated on Friday that the Delta variant was roughly 60 percent more contagious than the earlier one from Britain. Health officials also warned that cases caused by the Delta variant might lead to a higher risk of hospitalization, though it was too early to say for certain.
The divergent strategies of European nations and the United States also reflect broader differences in how Western governments are thinking about their responsibility to unvaccinated people, scientists said.
in unvaccinated pockets of the United States, where the virus continues to sicken and kill people at elevated rates. The Biden administration is still searching for ways to overcome that vaccine hesitancy.
In Britain, even with more than 90 percent of people over 65 having been fully vaccinated, health officials have resisted as speedy a reopening as they seek to expand inoculation rates in lower-income and nonwhite areas.
“We know the virus predominantly hits poorer communities and people of color hardest,” said James Naismith, a structural biologist and the director of Britain’s Rosalind Franklin Institute, a medical research center. “The U.S. strategy perhaps reflects a more deep-rooted commitment to individualism. The U.K.’s vaccination campaign is highly managed and mirrors more a sense of being our brother’s keeper.”
Britain decided last year to delay second vaccine doses to give more people the partial protection of a single dose. That helped it weather the wintertime surge but also left it potentially exposed to the Delta variant. Health officials said this past week that there was strong evidence of “a reduction in vaccine effectiveness” for the new variant that was most pronounced after a single dose.
Health officials have since changed the guidance to speed up second doses, but many scientists are urging the government not to commit to reopening until the impact of the variant becomes clearer.
76 percent overall have gotten one shot. As a result, some scientists say, upticks in new infections are tolerable so long as the vast majority do not lead to serious illness or death.
“This variant is going to find it hard to spread, because it’s limited to younger people and limited to certain parts of the country,” Professor Spector said.
He said the government needed to help the neighborhoods where it was spreading and, beyond that, encourage people to keep working from home and socially distancing when possible. But delaying the easing of restrictions, he said, was not necessary.
“We need to get used to the idea there will be a few thousand cases every day and that this is a part of our life,” Professor Spector said. “Those cases will be milder.”
Germany, France and Austria all moved quickly to bar most visitors from Britain.
Like Britain, the bloc was chastened by a surge of the variant from Britain this winter that contributed to one of the world’s highest death tolls. Governments were hammered for failing to cement the gains of last summer, when lockdowns were lifted across most of Europe.
In the bloc, 47 percent of the adult population has received a first dose, according to the European Center for Disease Prevention and Control, but only 23 percent have full protection.
For those reasons, European leaders have said that vigilance is needed, even though infections have fallen about 80 percent since mid-April.
“This progress is fragile,” Hans Kluge, the World Health Organization’s director in Europe, warned last month. “We have been here before. Let us not make the same mistakes that were made this time last year.”
Still, now that supply bottlenecks have eased, European officials are confident that 70 percent of adults will be fully vaccinated by July.
The quandary that Europe faces over how to react to the Delta variant may recur as the virus continues to evolve, some scientists said. As long as it remains in wide circulation, even more transmissible variants could emerge, forcing countries to grapple with whether to hunker down yet again or risk the virus spreading through unprotected populations.
Poorer nations are facing far more difficult choices, though. If the same sort of lockdowns that controlled the variant from Britain prove insufficient against this new one, those countries could have to choose between even more draconian and economically damaging shutdowns or even more devastating outbreaks. The Delta variant has already taken a horrifying toll on South Asia.
“Globally, it’s a nightmare, because most of the world is still not vaccinated,” said Jeremy Kamil, a virologist at Louisiana State University Health Shreveport. “It raises the stakes.”
The Indian government on Thursday said it had carried out 2.5 million coronavirus tests in 24 hours, the most in a single day since the pandemic began and part of an effort to try to help contain the spread of the country’s devastating second wave.
Balram Bhargava, the director general of the Indian Council of Medical Research, a top government body, said that in the last week, daily average testing had been between 1.6 million to 2 million tests. The government hopes to increase the number of daily tests to 4.5 million per day by the end of June.
India has been devastated by a surge in virus cases and deaths, many of which are believed by experts to have gone uncounted. The increase in testing has largely come from an uptick in use of rapid antigen tests. India’s health officials said they increased the share of antigen tests to 60 percent of the overall number of tests administered because labs have been overwhelmed and results from P.C.R. tests come with a longer wait.
Antigen tests are generally considered less reliable than P.C.R., and may mistakenly identify uninfected people as carrying the virus. But the virus is spreading to rural parts of the country where the health infrastructure is deeply underfunded. For some areas, rapid antigen tests are the only option because the distribution is in the hands of government.
said on Twitter. “Terribly worried that there is a Covid surge in rural India that is going largely unchecked & undetected.”
The council that Mr. Bhargava leads approved the use of a self-administered rapid antigen test kit that was developed by Mylab Discovery Solutions, an Indian company, and gives results in 15 minutes. The company is aiming to ramp up production to 60 million kits per month within the next few weeks.
“This easy-to-use test combines a mobile app so that a user can know positive status, submit the result to I.C.M.R directly for traceability, and know what to do next,” said Sujit Jain, the director of Mylab Discovery Solutions. “We are sure this small step will be a big leap in mitigating the second and subsequent waves.”
Vaccinating India’s population of 1.4 billion people is a challenge. At the current rate of administering about 1.8 million doses a day, it would take the country more than three years to vaccinate 80 percent of its population.
deaths from Covid-19 and Covid-related causes are likely to be two to three times the number that countries have recorded in their official data, because of the limited capacity of many countries to test their people and other weaknesses in official health data.
Once Americans return to crowded offices, schools, buses and trains, so too will their sneezes and sniffles.
Having been introduced to the idea of wearing masks to protect themselves and others, some Americans are now considering a behavior scarcely seen in the United States but long a fixture in other cultures: routinely wearing a mask when displaying symptoms of a common cold or the flu, even in a future in which Covid-19 isn’t a primary concern.
“I will still feel a responsibility to protect others from my illness when I have a cold or bronchitis or something along those lines,” said Gwydion Suilebhan, a writer and arts administrator in Washington who said he also plans to continue wearing masks in situations like flying on airplanes. “It’s a responsible part of being a human in a civil society to care for the people around you.”
Such routine use of masks has been common for decades in other countries, primarily in East Asia, as protection against allergies or pollution, or as a common courtesy to protect nearby people.
Meet the Press.”
Other leading American health officials, however, have not encouraged the behavior. The Centers for Disease Control and Prevention — which at the beginning of the pandemic advised against wearing masks, and only changed its guidance a couple of months later — does not advise people with flu symptoms to wear masks, and says they “may not effectively limit transmission in the community.”
That’s partly because there’s no tidy scientific consensus on the effect of masks on influenza virus transmission, according to experts who have studied it.
Nancy Leung, an epidemiologist at the University of Hong Kong, said that the science exploring possible links between masking and the emission or transmission of influenza viruses was nuanced — and that the nuances were often lost on the general public.
randomized controlled trials — the gold standard in scientific research — that masking reduced transmission of influenza viruses in a community.
There was some evidence from observational studies that masks reduced community transmission of influenza viruses, she added, but that research had a caveat: Observational studies cannot isolate masking from other possible factors, such as hand hygiene or social distancing.
“You can’t really decipher whether that observed reduction in transmission is due to face masks alone or not,” Dr. Leung said.
For similar reasons, the fact that the flu all but vanished in the United States during the coronavirus pandemic — and that many Americans anecdotally reported that they caught fewer colds than usual in 2020 — is not evidence alone that masks were responsible.
In East Asia, the historical use of masks is based on more than just medical research, and the steps that led each country to adopt them vary widely.
Please sneeze into your elbow, not your hand.)
Others pointed to institutional differences, including a history of anti-masking laws in the United States that were implemented during periods of social unrest in order to discourage violence.
New York State, for example, passed an anti-masking law in 1845 to prevent tenants from demanding land reform, according to research by Sharrona Pearl, a professor of medical ethics at Drexel University in Philadelphia. And from the 1920s to 1950s, several states passed similar laws in response to violence by the Ku Klux Klan.
Several East Asian scholars said in interviews that the region’s mask-wearing customs varied widely because people in each country had responded over the years to different epidemiological or environmental threats.
Jaehwan Hyun, a professor of history of Pusan National University in South Korea, said that ignoring the nuances could be dangerous.
seasonal dust storms that sweep into the country from Mongolia and northern China.
“Generally speaking, Koreans until recently believed that mask wearing was a sort of ‘Japanese practice,’ not ours,” he said.
In Hong Kong, where 299 people died during the SARS epidemic of 2002-3, the experience of universal masking against that coronavirus helped create a “cultural familiarity” with a practice that was also common during episodes of severe air pollution, Mr. De Kai said.
“It was a big reminder to people that masks are important not only to protect yourself from the pollution but also to avoid infecting those around you,” he said.
In Taiwan, SARS and recent air pollution were the two main factors that prompted people there to develop the habit of mask wearing, said Yeh Ming-Jui, a professor of public health at National Taiwan University in Taipei.
Professor Yeh said he believed mask wearing was not more widespread in the West because people there had no immediate memories of a severe pandemic — at least until now.
“The experience and health practices of past generations have been gradually forgotten,” he said.
Amy Chang Chien contributed reporting from Taipei.