The rapid spread of the delta variant across the U.S. in the past month has prompted fresh questions over whether reimposing indoor mask mandates will be necessary.
Los Angeles County health officials on Thursday responded to an uptick in cases by reimposing an indoor mask mandate on everyone, regardless of vaccination status.
The move by the nation's most populous county marked an escalation, as it came just two weeks after officials recommended masks as a precautionary measure. The county had lifted its previous mask requirement only about a month ago.
Public health experts largely agreed that L.A.'s decision to reimpose an indoor mask mandate was a wise decision but said it wouldn't make much difference without wider implementation.
Centers for Disease Control and Prevention Director Rochelle WalenskyRochelle WalenskyPfizer results offer hope amid worsening pandemic for children FDA panel endorses COVID-19 booster shots for older Americans, rejects widespread use Watch live: White House COVID-19 response team holds briefing MORE on Friday encouraged local officials across the country to consider similar preventative measures but indicated the agency would not be changing its own masking recommendations.
"These decisions have to be made at the local level," Walensky said during a White House briefing. "If you have areas of low vaccination and high case rates, then I would say local policymakers might consider whether masking at that point would be something that would be helpful for their community until they scale up their vaccination rates."
Walensky has repeatedly emphasized that vaccinated people remain at much lower risk of infection, even from the delta variant, which is why the agency is not going to change its guidelines that fully vaccinated people do not need to wear masks in most settings.
But there is no way to tell who is vaccinated and who is not without asking for proof, and the federal government has not given any kind of guidance or support to businesses that want to require proof of vaccination for customers and employees.
So while mask recommendations are technically still in effect for unvaccinated people, it's largely based on the honor system.
A mandatory indoor mask policy regardless of vaccination status may be a blunt instrument, but experts said that unless there's a widespread embrace of a certificate or passport system, it's the best way to protect both unvaccinated and vaccinated immunocompromised people.
"When you've got COVID cases rising and you've got a plateau in your vaccination coverage, that's a really blaring safety signal," said Lawrence Gostin, a professor of global health law at Georgetown University. "And the only way you can get on top of it is a mask mandate because except for vaccinations, universal indoor masking is the best tool we have in public health."
Gostin noted that if fully vaccinated people have enough exposure to the virus, they could also be at risk of getting sick. The more the delta variant circulates among unmasked, unvaccinated people, the more exposure vaccinated people have.
"Those cumulative exposures will make for more breakthrough infections and particularly for older, more vulnerable populations that could be at risk," Gostin said.
Delta is now the most common coronavirus strain in the U.S., making up more than 57 percent of cases in the two weeks from June 20 to July 3, which is the latest available data from the Centers for Disease Control and Prevention.
The delta variant is spreading among the country's large pockets of unvaccinated people, and health experts and public officials are warning that there will be localized spikes.
"This is becoming a pandemic of the unvaccinated," Walensky said. "We are seeing outbreaks of cases in parts of the country that have low vaccination coverage because unvaccinated people are at risk."
U.S. officials have been sounding the alarm for weeks that the delta variant is a risk to areas with low vaccination rates, which could undermine the hard-earned progress of driving cases down. Walensky on Friday said infections are up 70 percent, and hospitalizations are up 36 percent nationwide in just the past week.
But despite the clear risks from the delta variant, there was widespread agreement among experts that Los Angeles will be an outlier in reimposing masks.
"The places that arguably need the indoor mask mandates the most are the ones that are, in many cases, the least likely to implement them," said Leana Wen, a public health professor at George Washington University.
Both vaccine certificates and mask mandates are politically unpopular, which further reduces the likelihood of them being implemented.
Many Republican governors have banned local jurisdictions from implementing mask policies.
But they have also banned passports in any form, including from private employers, emphasizing that vaccination is a personal choice.
Scott Gottlieb, who was the Food and Drug Administration commissioner in the Trump administration from 2017 to 2019, told CNBC on Friday that he doesn't think L.A. made the right decision.
"I don’t think it’s the right move. I don’t think you can tell people who’ve been vaccinated that they have to wear a mask," Gottlieb said.
Forcing vaccinated people to wear masks could backfire, undermining confidence in the vaccine and creating a disincentive for the holdouts to get the shot.
But Gottlieb said there aren't really any good options right now.
"People who remain unvaccinated aren’t worried about the infection and don’t want to be wearing masks either," he said. "That means this is just going to spread through the population."