Masks protect against coronavirus infection, but with more than 84 million adults in the United States fully vaccinated against Covid-19, there are growing questions about whether wearing masks outdoors is still needed.
On Thursday, the director of the Centers for Disease Control and Prevention told "TODAY" the agency is considering revising its mask guidance.
“We’ll be looking at the outdoor masking question, but also in the context of the fact that we still have people who are dying of Covid-19,” Dr. Rochelle Walensky said.
Already in states where mask orders are still in effect, there are moves to loosen restrictions for outdoors. North Carolina Gov. Roy Cooper hopes to lift restrictions, including an outdoor mask mandate, by June 1. New York City Mayor Bill de Blasio is considering a change to outdoor mask guidance by June. Connecticut will lift mask requirements for outside in mid-May, along with transitioning indoor mask rules from mandate to guidance.
Some health experts are increasingly calling for mask restrictions to be eased for outdoor activities.
“We know that the virus largely spreads indoors and there's very little transmission outdoors, except in some very specific circumstances,” Dr. Ashish Jha, dean of the Brown University School of Public Health, said. “At this point in the pandemic, with more than half of Americans vaccinated, it's pretty reasonable to start thinking about peeling back outdoor mask mandates.”
Download the NBC News app for full coverage of the coronavirus outbreak
Masks should be used during large outdoor gatherings where people are close together for a prolonged period of time, such as a rally or sports events in packed arenas, he said. But passing someone on a street or going for a run without a mask is a very low-risk situation.
“Requiring everybody walking down the street to wear one is probably not needed,” Jha said.
A review paper published in The Journal of Infectious Diseases by researchers at the University of California, San Francisco, found that less than 10 percent of transmission occurs outdoors and the odds of spreading the virus indoors were 19 times higher.
However, experts at Northwestern University argue keeping masks on when you're outside — even after you're vaccinated — is not only a "social courtesy,” but also helps "model the behavior" for children, who can't yet get the shot.
According to current CDC guidance, “masks may not be necessary when you are outside by yourself away from others, or with people who live in your household.”
Health experts hope the CDC will more clearly outline high-risk situations when masks are truly needed.
Kristin Nelson, an assistant professor of epidemiology at the Emory University Rollins School of Public Health, said that while it was reasonable to include outdoor mask mandates up until now, she would like to see them be one of the first restrictions lifted as more of the population gets vaccinated and case counts start to fall.
“I think those mass mandates in outdoor spaces should probably be the first to go,” she said. “We really need to focus on places we know are at high risk for a transmission like large gatherings and closed spaces with poor ventilation.”
Homing in on the importance of indoor masking and helping people understand when it's safe to take off the mask may actually increase compliance, Jha said.
“Then you can really emphasize where it's not safe and get people to [wear their mask],” he said.
The rate of community transmission is an important factor for loosening rules. In places where it's lower, it may be an appropriate time to start lifting requirements.
Anne Rimoin, a professor of epidemiology at the UCLA Fielding School of Public Health, cautioned that setting a strict threshold to lift mandates isn’t advisable and that mask mandate metrics are subject to new and emerging science.
“If you're vaccinated and if there's low rates of community transmission, it's definitely reasonable to not worry about wearing masks [outdoors]” she said.
But when in a crowded situation or in close proximity to others, even if outdoors, it’s ultimately safer to keep the mask on, Rimoin said.