How to weigh your risks as mask mandates lift

Signs for mandatory masking came down at Logan Airport Tuesday and some passengers were maskless in the terminals.Suzanne Kreiter/Globe Staff

Now what? Airlines and public transit agencies have rushed to lift mask requirements after a federal judge’s decision on Monday to void the national mask mandate for planes, buses, and trains. The 10 largest airlines, the MBTA, and ride-sharing services Uber and Lyft quickly moved to make masks optional. The Biden administration plans to appeal the decision, but in the meantime, what should COVID-weary (and COVID-wary) people do? And how did one judge manage to overrule the CDC? We asked some experts. Here’s what they said.

Why did a federal judge strike down the federal mask requirement?

Based on a lawsuit filed in July by the Wyoming nonprofit Health Freedom Defense Fund and two Florida residents, US District Judge Kathryn Kimball Mizelle of Florida ruled that the Centers for Disease Control and Prevention lacked the authority to order the mask mandate. She rejected the agency’s claim it had the power to order the mandate based on a 1944 law, which was aimed at the prevention or spread of communicable disease. The judge, who was appointed by former president Donald Trump, said the law has generally been limited to quarantining infected people trying to enter the country and prohibiting the importation of diseased animals and does not give the CDC broad power to impose a sweeping mask mandate on all travelers.

Her 59-page decision, which noted that states hold the primary authority to institute public health measures, does not prevent states or local municipalities from imposing their own mask mandates.

Earlier Tuesday, when President Biden was asked during a stop in New Hampshire whether people should continue to wear masks, he said it is “up to them.” Then later in the day, the Justice Department said it would appeal the ruling “subject to CDC’s conclusion that the order remains necessary for public health.”

Does wearing a mask provide adequate protection even if people around you aren’t masked?

Yes, provided you’re wearing a high-quality mask such as an N95 or KN95, said Dr. Robert M. Wachter, professor and chair of the Department of Medicine at the University of California, San Francisco.

“Individuals have the tools to protect themselves quite well,” he said.

Wachter said that he doesn’t have any concerns about removing the mandate, but that he wishes the decision had been made by public health officials and medical experts. When a judge with little public health knowledge makes such a call, it sets “a dangerous precedent” that could limit the government’s ability to respond to future surges or pandemics, Wachter said.

Stephen Kissler, a postdoctoral fellow in immunology and infectious diseases at the Harvard T.H. Chan School of Public Health, said that even good-quality masks are not perfect, and that requiring everyone to wear a mask provides an extra layer of protection.

The experts interviewed were unanimous in urging people to continue wearing masks on public transit, for their own protection as well as that of others.

“Masking while traveling makes an awful lot of sense,” Kissler said. “I see it as a relatively low-cost and potentially high-benefit intervention.”

Which are safer — buses, trains, subways, or planes?

The difference, experts agreed, is not so much in the mode of transportation but the circumstances: whether the vehicle is well-ventilated, how crowded it is, how long the trip is, and what the transmission rates are in the community. A bus with windows open is safer than one with windows closed.

“Probably the most important factor is, ‘What are the chances the person sitting within a few feet of me has COVID?’ ” Wachter said. That can vary tenfold from one community to another, he said. On a plane, of course, with people from all over, you can’t estimate that probability.

Still, airplanes have excellent ventilation systems, with filters and frequent air changes while in flight.

But Dr. David H. Hamer, professor of global health and medicine at the Boston University Schools of Public Health and Medicine, cautions, “Even though there is very good air circulation once a plane is running its engines, during boarding when the engines are off, there is limited air movement or filtration so the risk is much higher.

“Trains, subways, and cars (taxi, Uber, Lyft) are lower risk but this really depends, too, on air flow (open windows where feasible will help),” he added in an e-mail.

If you’ve planned an airplane trip with children too young for vaccines or masks, should you cancel?

Depending on the circumstances, Wachter said, “I’d at least think hard about canceling it. . . . I think flying has become less safe today than it was two days ago. Not that it was perfectly safe before.”

For children ages 2 to 5, who are heading on an important trip, he’d take them if they could be trusted to stay masked. But if the trip can be postponed, it would make sense to wait until a vaccine is approved for that age group. For younger toddlers and babies, Wachter would cancel the trip — not because the child might get sick and die, which is highly unlikely, but because growing evidence suggests long-term harm from COVID exposure, including heart attacks, strokes, and diabetes.

“It seems there is less risk to children of acute disease, but we’re still learning a lot about long COVID,” Kissler said. He recommends consulting with the child’s pediatrician if the child has health issues that might put them at greater risk. Otherwise, “If you already had the travel booked, leaving from Massachusetts on a plane — I would feel OK about that.”

Should immunocompromised people travel?

They have options to protect themselves, Wachter said. Immunocompromised people can feel safe if they’ve had four vaccine shots, had an infusion of Evusheld (a treatment that boosts the immune system), wear an N95, and have access to antiviral treatments if they get sick. Taking those steps keeps the risk “very, very low,” he said.

The alternative is to tell immunocompromised people they can never travel again, because the current COVID-19 levels “are about as good as it gets,” Wachter said.

“There’s no reason I can think of that things will be much safer a year or two from now,” he said.

Will dropping the federal mask mandate lead to a spike in cases?

It appears likely, but it won’t be the only factor.

“It will contribute to an increase in cases, there’s no doubt about it,” Wachter said. But the lowering of masks everywhere will also contribute.

While most transmission occurs in crowded indoor places, travel “is a good way for getting the virus to mix around,” Kissler said. “Travel does help to link places and speed up the epidemic.”

But other forces are at play: New subvariants could increase cases, but increased outdoor activity in the warmer weather could slow transmission.

What will it take to get to the point that normal routines feel safe?

That will happen, Wachter said, when people simply get tired and stop talking about it. “I can’t see what would happen that would make the risk materially lower than it is now,” he said. “Maybe a better vaccine comes out, but how many people are going to take it? Maybe the [next] variant gets milder, but it’s just as likely it gets nastier.”

Andrew Lover, an assistant professor of epidemiology at the School of Public Health and Health Sciences at the University of Massachusetts Amherst, said in an e-mail, “Our ‘new normal’ may simply require masking for periods with increased transmission; it’s not the situation we’d all been hoping for, but the virus is still here and will remain a public health threat for the foreseeable future.”