Virus variant reignites debate on mask guidance

With a variant of the coronavirus rapidly spreading across the globe, masks are again the focus of conflicting views, and fears, about the course of the pandemic and the restrictions required to manage it.

The renewed concerns follow the rise of the delta variant, a highly infectious form that was first detected in India. It now accounts for 1 in 5 infections in the United States.

In May, federal health officials said that fully vaccinated people no longer needed to wear masks, even indoors. The advice signified a change in American life, setting the stage for a national reopening that continues to gain momentum.

But that was before the spread of the delta variant. Worried by a global surge in cases, the World Health Organization last week reiterated its long-standing recommendation that everyone — including the inoculated — wear masks to stem the spread of the virus.

On Monday, health officials in California’s Los Angeles County followed suit, recommending that “everyone, regardless of vaccination status, wear masks indoors in public places as a precautionary measure.”

Barbara Ferrer, the county’s public health director, said the new recommendation was needed because of upticks in infections; a rise in the number of cases from the delta variant; and persistently high numbers of unvaccinated people, particularly children, Black and Hispanic residents and essential workers.

Roughly half of Los Angeles County residents are fully vaccinated, and about 60% have had at least one dose. While the percentage of positive tests is still below 1% in the county, the rate has been inching up, Ferrer said, and there has been a rise in the number of reinfections among residents who were infected before and did not get vaccinated.

To the extent that Los Angeles County has managed to control the virus, it has been because of a multilayered strategy that combined vaccinations with health restrictions aimed at curbing new infections, Ferrer said. Natural immunity among those already infected has also kept transmission low, she noted, but it is not clear how long that immunity will last.

“We don’t want to return to lockdown or more disruptive mandates here,” Ferrer said. “We want to stay on the path we’re on right now, which is keeping community transmission really low.”

Health officials in Chicago and New York City said Tuesday that they had no plans to revisit mask requirements. Officials at the Centers for Disease Control and Prevention declined to comment but have not signaled any intention to revise or reexamine mask recommendations for those who are fully vaccinated.

“When the CDC made the recommendation to quit masking, it didn’t anticipate being in a situation where we might need to recommend masking again,” said Angela Rasmussen, research scientist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada.

“Nobody’s going to want to do it. People are understandably accusing them of moving the goal posts.”

But the delta variant’s trajectory outside the United States suggests that concerns are likely to intensify.

Countries in the Asia-Pacific region are reimposing restrictions and stay-at-home orders as the variant drives new surges. Four Australian ccities have reimposed lockdowns, and on Monday, the Malaysian government said nationwide stay-at-home orders would be extended indefinitely.

Even Israel — which has one of the highest vaccination rates in the world and is aggressively immunizing younger adolescents and teenagers who qualify — has reinstated mask requirements in public indoor spaces and at large public gatherings outdoors, after hundreds of new covid-19 cases were detected in recent days, including among people who had received both doses of the Pfizer-BioNTech vaccine.

This is not the first time the world has been consumed by a more contagious variant of the coronavirus. The alpha variant walloped Britain and brought the rest of Europe to a standstill earlier this year. In the United States, alpha became the dominant variant by late March, but the rapid pace of vaccination blunted its spread, sparing the nation a big surge in infections.

But delta is thought to be even more fearsome. Much of what is known about the variant is based on its spread in India and Britain, but early evidence indicates it is perhaps twice as contagious as the original virus and at least 20% more contagious than alpha.

In many Indian states and in European nations, delta quickly outpaced alpha to become the dominant version of the virus. It is on track to do the same in the United States.

Among the variant’s many mutations are some that may help the virus partly dodge the immune system. Several studies have shown that while the current vaccines are effective against delta, they are slightly less so than against most other variants. For individuals who have received only one dose of a two-dose regimen, protection against the variant is significantly reduced, compared with efficacy against other forms of the virus.

The WHO’s rationale for maintaining masking is that while immunization is highly effective at preventing severe illness and death, the degree to which vaccines prevent mild or asymptomatic infections is unknown. Officials at the CDC disagree, saying the risk is minimal.

The WHO maintains that vaccinated people should wear masks in crowded, close and poorly ventilated areas and should continue with other preventive measures, such as social distancing.

Even countries with relatively high vaccination rates have seen an increase in infections driven by the delta variant. Britain, where about twothirds of the population has received at least one dose of the Pfizer-BioNTech or AstraZeneca vaccine and just under half has received two doses, is nonetheless grappling with a sharp rise in infections from the variant.

It is not certain what course the delta variant will take in the United States. Coronavirus infections have been plunging for months, as have hospitalizations and deaths. But Dr. Anthony Fauci, the nation’s top infectious disease expert, has called the variant “the greatest threat” to eliminating the virus in the United States.

In May, when CDC officials lifted mask recommendations, they cited research showing that fully vaccinated people were unlikely to become infected with the virus, even with asymptomatic infections.

But the variant’s development of even partial immune evasion makes researchers nervous, as it suggests that fully vaccinated people may sometimes pick up asymptomatic infections and unknowingly spread the virus to others even if they never become ill.

The delta variant can infect vaccinated people, though its ability to do so is very limited, said Bill Hanage, epidemiologist at Harvard’s T.H. Chan School of Public Health.

“If you are in a place where cases are climbing, wearing a mask indoors in crowded public spaces is a way to keep yourself from contributing to the spread of delta,” he said.

Other scientists stop short of recommending that fully vaccinated people always wear masks indoors, but some now suggest that this may be appropriate depending on local circumstances — for example, wherever the virus is circulating in high numbers of people or where vaccination rates are very low.

Even now, roughly half of Americans are not vaccinated, and a wide swath of the country remains vulnerable to outbreaks of the virus and its variants. Vaccines for children under age 12 are not likely to be authorized until the fall at the earliest.