Outdoor Mask Wearing & COVID-19: Scientists Share Their Thoughts on the New CDC Coronavirus Pandemic Face Mask Guidance by 30Seconds Health

On Tuesday, April 27, 2021, the Centers for Disease Control and Prevention (CDC) issued guidance on outdoor face mask use for people who are fully vaccinated from COVID-19. The same day, SciLine asked three scientists questions regarding the outdoors and COVID-19, and the evolving coronavirus pandemic.

Q. What do we know about the likelihood of SARS-CoV-2 transmission outdoors?

“The risk of outside transmission is very low because viral particles disperse effectively in the outside air. A  study in Wuhan, China, which involved careful contact tracing, discovered that just one of 7,324 infection events investigated was linked to outdoor transmission. In a recent analysis of over 232,000 infections in Ireland, only one case of COVID-19 in every thousand was traced to outdoor transmission. And a scoping review from the University of Canterbury concluded that outdoor transmission was rare, citing the opportunity costs of not encouraging the public to congregate outdoors. Overall, transmission is around 5000 times less likely to happen outside than inside.” – Dr. Monica Gandhi, M.D., MPH, Infectious Diseases doctor and Professor of Medicine, University of California, San Francisco

“There is a significant amount of epidemiological data available that would suggest that outdoor transmission is unlikely. Further, there are several studies indicating that viral aerosols are likely to decay more rapidly outdoors. Together, this suggests that risk outdoors is low, and that reducing restrictions on mask wear during outdoor activities is reasonable.” – Dr. Joshua L. Santarpia, Ph.D., Associate Professor of Pathology and Microbiology at the University of Nebraska Medical Center and Research Director for Countering Weapons of Mass Destruction at the National Strategic Research Institute

“The CDC just changed the guidelines today, and what they’re saying is that if somebody is outside, you don’t have to wear a mask. And that’s a relief for people who do a lot of outdoor activities. The ambiguity is gathering size, because a lot of people are worried about what gathering size they’re talking about.” – Dr. Asim Shah, M.D., Professor of Community and Family Medicine, Professor of Psychiatry, Baylor College of Medicine

Q. Based on the new CDC guidance, how should people decide what size "small group" is acceptable for maskless gatherings outdoors?

“For vaccinated people, the group can be quite large and likely depends on case rates in your region (case rates are falling across the U.S. with a  -20 percent decrease in new cases per day over the past two weeks in the U.S.). This is because vaccines are extremely effective in real-world settings. The CDC keeps track of breakthrough infections – where people contract COVID-19 after vaccination – in the U.S and the rate remains astoundingly low even while COVID-19 is still circulating (32,151 cases across the U.S. today). Out of 87 million fully vaccinated people, there have only been 5,079 symptomatic breakthroughs (0.005 percent), only 0.0003 percent hospitalizations related to COVID-19, and only 0.00009 percent deaths related to COVID-19. Vaccines are incredibly effective under real-world conditions.

“The risk to unvaccinated people is higher and depends on the case rates in your region. I would recommend that unvaccinated people in crowds or packed situations put on their masks. I think this signals a great time in the pandemic in our country. However, this is a terrible time in the pandemic for India, where only 8.8 percent of the population has had their first dose of the vaccine. Cases stay low in countries that are opening up, like Israel and the United kingdom, if vaccination rates are high – Israel has  60 percent of their population vaccinated with their first dose and the United Kingdom has 51 percent of the population first dose vaccinated (the U.S. is at 42.7 percent first-dose vaccinated). Relaxing masking outdoors will not lead to increased cases in our country as we continue to vaccinate, but my heart bleeds for India and we should do everything we can to help this country and other regions of the world who do not have the same access to vaccines.” –Dr. Monica Gandhi

“This is a pretty vague recommendation, and it requires people to make their own risk assessment. People have to make decisions about how closely they might interact with others at gatherings. There’s not a clear line, and no answer will be without risk, so it’s up to the individual to make the best decision they can.” – Dr. Joshua L. Santarpia

“The definition of ‘gathering’ is vague, and what the CDC is saying is that a large gathering is considered large when you have many people from multiple households in a private or a public setting. So, if you have multiple people from different households, you have maybe 25 or 30 people, that would be considered large, whereas the same number of people from the same household would not be considered large. So it’s not an absolute number, it’s how many households you are covering. Because each household brings an added chance of COVID.” – Dr. Asim Shah

Q. Should partially vaccinated people follow the same masking guidelines as unvaccinated people?

“There are two principles involved to changing the outside mask guidelines: One is that COVID-19 transmission outdoors is very low. The second is that – with more and more Americans getting vaccinated – recommending that vaccinated people could congregate outdoors without a mask can be a motivating factor for those on the fence about masking. The World Health Organization, even prior to vaccines, stated that masks are not necessary outside unless it is impossible to maintain physical distancing (defined as 1 meter = 3.28 feet by WHO guidelines), so unvaccinated people should be able to unmask outdoors if they can maintain 3 feet of distance from others. For situations such as rallies and packed outdoor events, I would recommend unvaccinated people mask until case rates are lower than 5 per 100,000 in your region. And I would recommend partially vaccinated people follow the same guidelines as unvaccinated.” – Dr. Monica Gandhi

“Partially vaccinated individuals have some antibodies, have some immunity to the virus, and some protection against infection and disease. That said, it’s the safest option to behave as if you are unvaccinated, if you have only had a partial vaccine.” – Dr. Joshua L. Santarpia

“Partially vaccinated people are considered nonvaccinated. So you are only considered vaccinated two weeks after your last dose of vaccine. Partially vaccinated there is no difference than nonvaccinated, so you should follow the same guidelines as a nonvaccinated person.” – Dr. Asim Shah

Q. How might differences in public masking behavior between vaccinated and unvaccinated people impact wider masking behavior or public perceptions of what is safe?

“I know that many public health practitioners have argued the ‘slippery slope’ principle that we will not be able to mask indoors if guidelines change to allow unmasking outdoors. But I argue that Americans know when they are outside and can understand this nuance. Moreover, since outdoor transmission is so low anyway, even for the unvaccinated, I am not concerned this will increase case rates or public perception of what is safe. Indeed, I think following the data on how low the risk of outside transmission is and being consistent with WHO guidelines increases trust in our public health guidelines.” – Dr. Monica Gandhi

“It’s certainly something to consider. I believe that people need to take individual responsibility for their own safety. Everyone needs to make their own personal risk assessment, based on vaccination status or previous infection, co-morbidity factors and situation. Further, they need to appreciate that someone else’s risk calculation may be different and so they may behave differently. As long as we establish some general guidelines, there is room for variation.” – Dr. Joshua L. Santarpia

“One of the reasons that the CDC issued these guidelines is to give people incentives to go for vaccination, because now we have 20 percent or more of Americans who don’t want the vaccine. So we want to give people an incentive that if they are vaccinated, they can go out and don’t have to wear a mask and are okay. So that’s one of the reasons. The problem with masking that we are facing right now is the concept of autonomy. A lot of people do not want to mask because they feel that, oh, it’s an infringement of my rights. But this is a public health issue, so we need to think differently.” – Dr. Asim Shah

What do you think about the CDC's guidance on outdoor face mask wearing? Tell us below!

Source: SciLine press release

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