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Nov 25, 2023

Face masks are one of the most crucial measures to prevent the spread of COVID-19, but confusion and misinformation still surround their use.

In this new phase of the pandemic, in which about 70 percent of Americans have had at least two shots of a COVID-19 vaccine, many may be tempted to ditch masks altogether. But is that the best option? There's a new, and fast-spreading omicron subvariant, popularly dubbed "Arcturus," gaining traction in the U.S. It's estimated to account for about 15 percent of all recent COVID-19 cases nationally, the CDC reported in May.

So, if to mask or not to mask is your question, we asked UC San Francisco's Peter Chin-Hong, M.D., an infectious disease expert, for the answer.

Chin-Hong: If you want to protect yourself from COVID-19, the most important thing you can do is stay up-to-date with the vaccine. Research shows COVID-19 boosters are about 70 percent effective at preventing serious COVID-19 and hospitalization. Taking Paxlovid or other therapies like remdesivir early in the course of infection can also reduce the risk of hospitalization even if you are unvaccinated.

If you’re up-to-date on the vaccine but still wondering if you need to mask, then I’d say it depends on who you are, who you live with and the context.

When hospitalizations are high, everyone should wear a high-quality mask. But when we’re seeing medium numbers of hospitalizations, people at high risk for serious COVID-19 should mask in crowded indoor settings like public transportation and airports. This would include people who are older than 65, immunocompromised, unvaccinated or not up-to-date on their booster shots. At low levels of hospitalizations, people can choose to wear a mask at any time, particularly in the setting of indoor public transit. If you live with someone at high risk, you should also consider masking to help protect them — even if you are up-to-date with your vaccines.

In California, you can check the level of COVID-19 hospitalizations in your county.

Places where infections spread quickly, like hospitals, shelters and assisted living facilities may continue to mandate mask use, regardless of how many cases we see.

Of course, if you suspect you have COVID-19 or have been diagnosed, you should always wear a mask for at least five days.

Chin-Hong: Face masks are highly effective at reducing COVID-19 transmission, especially when a high-quality mask is used with other preventive measures like social distancing and frequent handwashing. No face mask provides 100 percent protection and not all masks are created equal.

Chin-Hong: The virus that causes COVID-19 spreads primarily through respiratory droplets — or tiny drops released into the air when an infected person talks, coughs or sneezes that can also settle on surfaces. These droplets can infect others if they come into contact with the nose, mouth or eyes through the air or if someone has touched a contaminated surface and then touched their face. A mask helps to block these droplets from spreading, which reduces the risk of transmission.

Chin-Hong: Medical N95, KN95 and KF94 masks all filter out lots of particles from the air and are the best at protecting against COVID-19. Avoid masks with valves, which allow a wearer's breath to pass out unfiltered, spreading germs.

Disposable surgical masks are less effective but still reduce your COVID-19 risk especially if well fitting.

Cloth masks aren't recommended but are better than no mask. Wearing a surgical mask beneath a cloth mask makes it more effective.

Chin-Hong: The mask should cover your nose and mouth and fit snugly against the sides of your face without gaps. Wash your hands before putting on your mask and avoid touching it while wearing it. Remove the mask by the ear loops or ties and avoid touching the front of the mask.

Chin-Hong: Clean and undamaged N95, KN95 and KF94 masks can be reused for a few days. Surgical masks are meant for one-time use, but a reused surgical mask is better than no mask. Cloth masks should be washed after each use with soap and water and dried. If you have access to a dryer, dry the masks on a high heat setting.

Chin-Hong: Wearing a mask for a long time can cause skin irritation or acne, but these can be prevented by using a clean mask and properly washing and moisturizing your face.

Chin-Hong: No, wearing a face mask does not cause carbon dioxide poisoning. The amount of carbon dioxide that accumulates inside a mask is negligible and not harmful to the body.

Chin-Hong: If you are 12 years or older and at high risk of developing serious COVID-19, find out if you’re eligible for the antiviral medication Paxlovid by talking to your health care provider or pharmacist. If taken within the first five days after symptoms start, Paxlovid can stop the virus from replicating and reduce your chances of developing serious COVID-19. Remdesivir and molnupiravir are other options.

Paxlovid can prevent being hospitalized with COVID-19 by as much as 90 percent if you are at high-risk for the development of serious disease. It also reduces the risk of "long-COVID," a condition with symptoms like shortness of breath, "brain fog" and even mood changes that persist for weeks after a person recovers from an initial COVID-19 infection.

COVID-19 is here to stay so wearing a mask is a cheap and easy way to avoid getting infected and having to stay home. It can also help protect you from colds and flu.

Peter Chin-Hong, M.D., infectious disease expert

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