If you’re vaccinated, “I’d say for the most part, you don’t need to wear a mask outdoors,” Dr. Sanjay Gupta said Thursday on CNN’s New Day.
That’s because it’s known most viral transmission doesn’t happen outdoors.
A November review in the Journal of Infectious Diseases found that the odds of viral transmission are 18.7 times greater indoors than out, and less than 10% of Covid-19 infections studied occurred outside.
Nooshin Razani, one of the authors and an associate professor of epidemiology and biostatistics at the University of California, San Francisco, told Slate the true number of instances of outdoor transmission was “probably lower” than 10%.
Current guidance from the US Centers for Disease Control and Prevention makes it clear masks might not be needed outside. “Masks may not be necessary when you are outside by yourself away from others, or with people who live in your household,” it says. The CDC does not say anything specific for vaccinated people.
To Mask or Not to Mask?
As with most Covid-19 discussion, the evidence on whether it’s advisable to wear masks outdoors isn’t black and white, and should be based on a variety of factors such as vaccination status and community transmission rates.
“If you’re vaccinated and not in a vulnerable category, it’s probably fine not to wear a mask outdoors,” Linsey Marr, an expert on the airborne transmission of viruses at Virginia Tech, told CNN in an email.
For unvaccinated people, Marr recommends masks in situations when people are clustered closely together, like in a bar, a crowd or a line.
“If you’re unvaccinated and constantly passing by people close enough that you can reach out and touch them, then you should wear a mask,” Marr told CNN.
Vaccinated or not, an important factor in deciding to unmask outdoors is the levels of transmission and positivity in your area, Gupta said.
“The real question you need to try to answer is, what is the likelihood I’m going to breathe in someone else’s air? That’s basically it. The number of people, type of setting and what is the overall viral spread in their community,” Gupta said.