When should vaccinated people wear masks now? An expert weighs in

The Delta variant, a more transmissible – and potentially more dangerous – strain of coronavirus, now makes up more half of all new infections in the United States, according to the US Centers for Disease Control and Prevention.

This variant, combined with low rates of vaccination in many parts of the country, is leading to new surges in Covid-19 cases, which has led to Los Angeles County and St. Louis-area health officials encouraging even people who are fully vaccinated to wear masks indoors. The World Health Organization has issued similar guidance (the CDC has continued to say that vaccinated people do not need to wear masks under most circumstances).

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To clear up confusion about masking, we turned to CNN Medical Analyst Dr. Leana Wen for her thoughts. Wen is an emergency physician and visiting professor of health policy and management at the George Washington University Milken Institute School of Public Health. She’s also author of a new book out later this month, “Lifelines: A Doctor’s Journey in the Fight for Public Health.”

CNN: Are there circumstances in which vaccinated people should return to wearing masks indoors?

Dr. Leana Wen: Yes. Masks are still required in some settings, such as airports, on planes and trains, and in hospitals. If a business requires masks, you should still wear a mask, so it’s a good practice to carry a mask around with you in case you need it.

The more difficult question becomes, what about settings where you don’t have to wear a mask – when might you choose to wear one? Here are the factors I’d consider.

First is your health and the vaccination status of those in your household. If you are immunocompromised, you should be wearing a mask in all indoor settings where you could be exposed to unvaccinated people.

If you live with someone who is immunocompromised or with young, unvaccinated children, you might still want to take additional precautions. Your chance of contracting Covid-19 and passing it on to your family is much lower once you’re vaccinated, but it’s not zero. Consider wearing a mask in high-risk settings, such as crowded grocery stores or indoor church services.

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Second is the level of coronavirus infection and the rate of vaccination in your community. These two are generally correlated: The areas with higher rates of vaccination also tend to have lower levels of infection.

If you’re living in an area where over 80% of adults are vaccinated, and the Covid-19 rates are very low, your chances of encountering an unvaccinated, infected person is greatly reduced. You are probably safer going without a mask there compared to, say, if you’re living in an area with less than 30% of adults vaccinated and where the Delta variant is surging.

CNN: Some people reading this will ask, “Why are we even talking about masks again, when the vaccines are supposed to work so well?”

Wen: The Covid-19 vaccines we have in the US do work very well. But no vaccine works 100% of the time. Think of the vaccine as a very effective raincoat. If it’s drizzling, you’ll be protected. If the rain is coming down hard, you might still be fine. But if you are going in and out of rainstorms all the time, you could end up getting wet.

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Risk is cumulative. If you have multiple encounters every day with unvaccinated people, and there is a high level of community transmission in your area, your chances of having a breakthrough infection after vaccination will increase. You can reduce that risk by wearing a mask in the highest risk settings.

CNN: What if you’re going to work and everyone in your office is vaccinated? Do you still need to wear a mask if there’s no distancing?

Wen: Good question. We know that vaccination dramatically reduces your likelihood of becoming infected and of being an asymptomatic carrier who could transmit the virus to others. Your chance of becoming infected from a vaccinated person, if you’re also vaccinated, is virtually zero. Going to an office where everyone around you is known to be vaccinated, even without masks and distancing, is very safe.

CNN: What about the reverse – what if you have to be back at work, but vaccinations aren’t required? Should you mask up?

Wen: That depends on the other factors we discussed. Consider your health, then the likelihood that someone at work could be infected based on community transmission and vaccination rates in your area. Also consider the circumstances at work. Are the people you are in close contact with vaccinated? Let’s say that your workplace doesn’t have a vaccination policy, but the two people who share your office or the three people with cubicles closest to you are fully vaccinated. That would be a pretty safe environment, and you probably don’t need to be wearing a mask at your desk.

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On the other hand, if you are asked to go into cramped, poorly ventilated conference rooms with people who you doubt are vaccinated, consider wearing a mask there, or, better yet, see if you could attend the meeting virtually.

CNN: Does the type of mask matter?

Wen: If you are immunocompromised and are in a high-risk setting, you should be wearing an N95 or KN95 mask or double-masking. Otherwise, a well-fitting 3-ply surgical mask should be sufficient, though if you’re comfortable with the N95 or KN95, there is no harm to wearing that in crowded indoor settings.

CNN: Are there any outdoor settings where you’d recommend a vaccinated person wear a mask?

Wen: Not at the moment. The ventilation that comes with being outdoors reduces transmission so much, as does vaccination. A person who is severely immunocompromised may still wish to wear a mask at crowded ball games or concerts, but otherwise, outdoor masking should not be needed for vaccinated people.

CNN: What if people assume that you’re unvaccinated because you’re putting on a mask?

Wen: A lot of people who are vaccinated and want to be extra cautious are wearing masks. It could even be that the people wearing a mask in public places are actually vaccinated, and it’s the people who are unvaccinated who are walking around unmasked. You should focus on doing what makes you comfortable. If you’d feel more comfortable wearing a mask in some settings, you should do that.

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CNN: How does the Delta variant affect your recommendation?

Wen: Now that more than half of new infections in the US are caused by this variant, you should assume that if you were to come into contact with someone with Covid-19, it’s the Delta variant you’re encountering. This variant is more transmissible than any of the previous variants. There is some evidence that those infected with the Delta variant also carry more virus, thus making them more likely to infect others. The vaccines we have do appear to be effective against the Delta variant, though less effective than they are against other strains.

CNN: To be clear, unvaccinated people still need to wear masks?

Wen: Right. The guidance for unvaccinated people has not changed. If unvaccinated people are around other people who are unvaccinated – or people who are of unknown vaccination status – they should be wearing masks indoors. Outdoors, the risk of transmission is low, so no masks are needed there. This applies to kids too, so children under the age of 12 who are not eligible to be vaccinated should still be wearing masks indoors when around other unvaccinated kids.

With the Delta variant on the rise, I would be even more vigilant than before. If there is a situation where you’re on the fence about whether to put on your mask, I would err on the side of caution and just do it.