Megan Ranney, MD, MPH, is an associate professor of emergency medicine at Brown University and co-founder of Get Us PPE. The opinions expressed in this commentary are her own. View more opinion on CNN.

(CNN)On Tuesday, the US Centers for Disease Control and Prevention released new guidance on mask-wearing. While the guidelines cover a variety of scenarios, there are two key changes. First, it is now perfectly safe to be unmasked outdoors, regardless of vaccination status, if you are with members of your household or attending a small gathering where everyone else is fully vaccinated. Second, and more importantly, these new guidelines reaffirm that people who are fully vaccinated can safely go unmasked in almost any outdoor scenario — the exception being crowded events like live performances or parades. The guidance for everything else (including recommendations to continue wearing masks indoors) has essentially stayed the same.

Megan RanneyMegan RanneyMegan RanneyDespite the incremental shift in official guidelines, my phone blew up almost instantly with questions, concerns and political statements. Messages ranged from confused (“Is this safe? I don’t even know who to trust any more!”) to frustrated (“Why couldn’t they have said this months ago?!”).I will tell you what I have told each of my friends and colleagues: These recommendations are scientifically sound, absolutely safe and unsurprising to those of us in public health. They accord not only with the latest research, but also with the guidance being followed by the rest of the world. You can follow these rules without worry. But you should also prepare yourself for more change to come, especially if you’re vaccinated. Read MoreHere’s why: First, the difference between the CDC’s recommendations for indoor and outdoor masking reflects what we now know about the virus: It spreads primarily through the air. Imagine that you’re near someone who is smoking a cigarette. If you’re indoors, the smoke — just like a plume of respiratory droplets and aerosols — can linger in high concentrations in the air for extended periods of time. In the case of Covid-19, this persistent plume of viral particles is what creates a higher risk of infection. If you’re outdoors, however, the breeze quickly dilutes the concentration of infectious virions, just as it would smoke from a cigarette. The Covid disaster in India shows that the future is biological, not digitalThe Covid disaster in India shows that the future is biological, not digitalThe Covid disaster in India shows that the future is biological, not digitalThe only time outdoor activities are potentially risky is when you’re in a crowd and social distancing from unvaccinated people is not possible. Again, imagine the situation with a cigarette. If you’re packed in a crowded stadium next to someone who’s smoking, you’re going to smell it for a while, because the breeze won’t be able to dissipate the smoke as easily. The same holds true for Covid-19. If a sick person standing next to you in a crowd coughs, it can be tough to avoid the viral plume, even if you’re outside. Being in a closed room is still riskier. Without great ventilation, those viral particles will stay in the enclosed air, putting you at an even higher chance of getting infected.Unless, of course, you can keep the virus from reaching you. Well-fitted masks do exactly that. For the infectious, masks reduce the chance of transmitting the virus to others; for everyone else, masks can reduce the chances of breathing it in. So, masks remain important in places with poor ventilation and air flow, whether you’re indoors or in a crowd outside.This is why the CDC’s recommendations for masking distinguish between outdoor activities among small groups (which poses the lowest risk for everyone), outdoor activities where large crowds make it impossible to maintain social distancing (mild-to-moderate risk) and indoor activities (higher risk). The second important piece of the science behind these recommendations, of course, is the vaccines. Covid 19's lessons are key to crushing the world's most brutal infectious diseaseCovid 19's lessons are key to crushing the world's most brutal infectious diseaseCovid 19's lessons are key to crushing the world's most brutal infectious diseaseThe vaccines that are approved in the United States work amazingly well. If you’re fully vaccinated, and you’re around other vaccinated people, the chance of being infected with the SARS-CoV-2 virus is almost nil. This is why the CDC’s new recommendations are more relaxed for people who are fully vaccinated than for those who aren’t. I can’t emphasize this strongly enough: These vaccines are our ticket to normality.Why, then, does the CDC still recommend masks for vaccinated people in some situations? It’s largely because there are still so many people in this country who aren’t vaccinated. And while the vaccines are highly effective, they do not provide a 100% guarantee. The more unvaccinated people you’re in a room with, the higher the chances are that someone in that room is sick. What I wrote about the importance of masks, whether it was a month ago, or a year ago, still holds true. They work. And for now, they are still recommended indoors even if you are vaccinated.But the efficacy of vaccines is also why I am already telling my friends to stay tuned for more changes. As more of us get vaccinated, the rate of infection will continue to drop — which means the chance of being exposed to someone who’s sick will drop, too. At the current rate of vaccination, it’s likely that masks will not be necessary in most circumstances, for most Americans, by early summer — assuming there are no horrible new variants. Get our free weekly newsletter

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Of course, as I told my friends on Tuesday, even if you are no longer required to wear a mask, you still can choose to wear one. In Hong Kong and Japan, for example, mask-wearing on public transportation and in crowded public spaces has been a norm — not a requirement — for years. For people who are immunosuppressed (for whom the vaccines may not be as effective) or otherwise high-risk, it might be a good idea to choose to continue wearing a mask, especially indoors, regardless of the regulations.So: Breathe easy. The CDC recommendations make sense. And now, if you so choose, you can breathe easy without a mask outside.But please, please, get your shot — so we can all do our part to defeat Covid-19.

Source Link:
https://www.cnn.com/2021/04/30/opinions/science-behind-new-cdc-mask-guidance-ranney/index.html

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