Dr. Wachter Weighs In: To Mask or Not To Mask?

Monday, March 7, 2022

Dr. Bob Wachter, UCSF’s Chair of the Department of Medicine, gained a vast twitter following during the COVID pandemic with his informative, direct, and sometimes personal tweets. He’s kept his followers up to speed throughout changes in the science, vaccination rates, and spread of infection. And as issues around the pandemic evolved, so did his position. In our latest podcast episode, we asked Dr. Wachter for updates on masking, transmission rates, and possible new variants.

Read the transcript below.

Janice Goh

Thank you so much for doing this with us. Could you tell us a about your role regarding the COVID pandemic at UCSF?

Dr. Bob Wachter

I'm Chair of the Department of Medicine. So that's the largest department and I've got about 900 physicians in my department, about 2,500 people. And when COVID launched and became a problem in the United States in March 2020, it became clear to me that people are going to be hungry for information. And that as a senior leader at UCSF, I had access to a lot of information and access to some of the world's experts in the various components of it. I was already on Twitter and probably had 15,000 followers at the time. I thought there might be interest in someone who kind of took all of the information that was emerging and pulled it together and tried to explain it.

And so, I started doing that. And lo and behold, it was like on that. Just like in the movies, I started seeing the like button spinning as more and more people began following me. People seem quite interested in my tweets. Most of my tweets are me being somebody who tried to be thoughtful about where the pandemic was, keeping track of the literature, getting some of the most interesting and hardest questions answered, and then processing it, and putting it in a way that out there in a way that people found accessible.

I've also, to some extent, been comfortable being a little bit personal. So telling people, you know, here's what I am personally doing, and I'm am or I'm not willing to travel now, or I am or I'm not wearing a mask in these circumstances.

And I think some people have found that useful, because they just have been so confused by conflicting information that they were looking for somebody who was they thought was a credible source. And I've had many people say to me, I'm just doing what you're doing and keep telling me what you're comfortable doing now. So it's been pretty gratifying.


What are your opinions on removing the mask mandate that has ended for adults on February 15th?

Dr. Wachter

I thought that vaccine mandates and mass mandates were completely appropriate earlier in the pandemic. In the United States, or in any political system, there's always this tension between individual liberties and the rights and obligation of the government and authorities to sometimes mandate things.

You know, none of us want to pay taxes, none of us necessarily don't want to speed or stop at stop signs. But there's a role for the system saying you have to do certain things because your behavior influences others. And to me, a pandemic like this, that was killing hundreds of thousands of Americans was a circumstance where, where the balance of the benefits of mandates for things that are not only good for the individual, but good for the collective outweighed the assumption of people having the individual choice and individual liberty.

We then reached a point in the legislature really in the last month, and largely because of Omicron, that when the threat falls to or below a certain level, the benefits of mandates are less than the downsides of mandates.

And I think we're at that level now, where we know that everybody who has had three vaccine shots are incredibly well protected, and that the level of COVID in our community is now quite low and falling. We know how incredibly protective wearing a good mask is, and most people have access to N95 or the equivalent KN 95 or KN94s. Furthermore, the current variant is not as severe as the prior variants.

The ability of everyone to have gotten very well protected with shots if they wanted to, and the ability of people to continue to keep themselves protected with a good mask. means that the case for mandates has gone down. I still believe that working in a healthcare organization, for example, where you have a lot of vulnerable patients the balance of is such that mandating that people are fully vaccinated and people wear masks outweighs the downside.

But in terms of day-to-day life, I think it is perfectly reasonable to say that it no longer should be mandatory that you wear a mask when you go shopping, or in or in the schools. But people should have the opportunity and be perfectly free to do that.

So for me, for example, I now am comfortable eating in an indoor restaurant, obviously not wearing a mask. But when I go to the Safeway, or go, you know, go shopping, I will continue to wear a mask because I think there's I don't see any real benefit not wearing a mask and the risk of me getting COVID is not zero.

But giving people the individual choice to make those choices to me is reasonable. Whereas earlier in the pandemic, it was perfectly reasonable for the state to use its authority to mandate certain things.


To use the N95 effectively, which is what's really protective from Omicron, we actually needed to get a mask fitting. Currently, it's easy to get the N95. But it's not that easy to get a proper fit. Like, I'm just wearing it based on the guess that I am an S size, for example. So will that actually affect the effectiveness?

Dr. Wachter

A little bit? Yeah, I think, you know, one of the things that people get confused about with cognitively, for people that don't have a scientific or medical background is many of these questions are not binary. They're not, you know, yes or no, the vaccines work, yes or no, do masks work, yes or no? Is it safe to not wear a mask? Yes or no.

In actuality, they really are all probabilistic. And that's something as a physician I'm very comfortable with because that's how we're trained. But for laypeople, I think it was very difficult to get their arms around. And you know that it's not binary, it's really you know, that they work. But certain things work better and certain things work worse.

The risk changes as the prevalence of the virus in the community go down. So, what we now know, and we didn't know very well, in the beginning was, masks are protective, but not their level of protection. Depending on the kind of mask you wear, they can be more or less protective. Probably the best estimate is that a cloth mask is 20, or 30% protective, and a surgical mask is 40 or 50% protective. The N95 that's not fitted is probably 80 or 90%. protective, and N95 that is fitted and health care grade, is 95 to 98%. Protective. So if you're wearing a nonfitted KN94 or 95, which is what I wear in the hospital, most of the time, your level of protection is very, very good, but not perfect.

So when I'm in the wards, I generally am wearing the nonfitted KN95, which is very comfortable. And when I go into the room of someone I know as COVID, I take it off, and I put on the better mask because I think the probability of me being exposed to COVID. So I want to wear the best possible mask. So the in the same way that it wouldn't be ridiculous for someone now to go shopping, and wear a surgical mask to say I've lost some protection compared to an N95.

But the chances I'm going to have someone next to me in line at the Safeway who has COVID is, you know, orders of magnitude lower today than it was a month ago. And he might be willing to have a little bit less protection because the protection will be tested far less often than it would have been when we were at the height of the surge.


What do you think about not just daily activities like going shopping, but things like mass gatherings? For example, like going clubbing or weddings or religious gatherings?

Dr. Wachter

Yeah, I mean, "Is it safe?" has no answer to it. You know, it really is,"Is it safe enough? Is it safer than it was?" I can only tell you sort of how I think about it.

My personal feeling is that if I were in a community like San Francisco, where we're down to a level of virus that's about 10 cases per 100,000 people per day, then going to a wedding with 50 to 100 people that's maskless, I would be very comfortable. If everybody was vaccinated and boosted, I would be even more comfortable, and if I knew people had done a rapid test a couple of hours before.

If I didn't know either of those things, I would think that the risk is small but not zero. And I would then go to my own personal risk. So as a pretty healthy 64-year-old guy, I probably would do it if it was really important to me.

But if it was someone whom I wasn't that close with, I probably wouldn't. If I was an 80-year-old, I probably wouldn't. If I was a 30-year-old, healthy person, I probably wouldn't think twice about it. So it's not only the risk of getting COVID. But the risk of having a bad outcome if I did get COVID. And even those numbers may change six months from now, because Paxlovid will be more generally available, which lowers the probability of a bad outcome by 90%.

If you think about the risk for an 80-year-old, it's the risk of getting COVID, and then a risk of a bad outcome. If I got COVID, and could immediately go on a medicine, and have access to medicine that lowered my chance of bad outcome by 90%, then I might say it's worth the risk. So that's why this is so incredibly complicated because there really is no answer to is it safe.

Safety depends on the prevalence in your community and also your own personal risks of a bad outcome with COVID. And I could see two different people looking at that, and coming up with different conclusions whether it's safe enough.


How do you come up with the figure of less than 10 cases per 100,000? How did you define that threshold?

Dr. Wachter

I mean, it's a number that public health experts in the CDC have tended to use. It's made up, because there's no bright line at 10. Ten is safer than 15 and less safe than 5.

Where does it come from? In general, it's associated with a level of virus and a community. That means there's a relative there's very little community spread, it almost always means that hospitalizations are very low, and therefore, hospitals are not overstressed. It has tended to correlate as you've looked at surges, and then lulls in the pandemic, when you get to 10 cases per 100,000 per day.

So in a city like San Francisco with 875,000 people, that would mean there's about 80, or 90 cases a day in San Francisco. That usually correlates with test positivity as well.

One of the numbers I like to look at is UCSF asymptomatic, test positivity rate. It is not a national number, but it's actually a nice thing that we have at UCSF, because we test everybody who's coming in for heart surgery, or for colonoscopy, or for hospitalized for asthma, something that has nothing to do with COVID.

It's essentially about as close as we can get to, what are the chances that someone who has no symptoms of COVID in San Francisco, is carrying the virus. And when you get down to about 10 cases per 100,000 per day, that number tends to be about half a percent. So that's not zero. So it means that if I'm standing in line at the Safeway, there probably is a one in 200 chance that the person standing next to me in line has COVID, which is why I'm probably still going to be wearing a mask there because it's not zero. But it's a low enough number, that if you're deciding to go out for dinner and be in a crowd of 10 people around you plus your waiter.

If the overall prevalence among asymptomatic people is one in 200, the chances that any person within a group of 20, 5 - 10% chance that somebody's positive, it's not zero. But it's low enough that I think most people who are using it as a threshold that my risk of getting infected in a place where I'm hanging around with a few people whose status, I don't know is very low.

But again, there's this there's no bright line. I would say somebody's at higher risk of a bad outcome such as an immunosuppressed person might say 10 is too high, I need that number to be closer to one or two. While someone who's a healthy 30 year old person might say I'm perfectly comfortable with a number of 20 or 30. 

But if it's 100 people per 100,000 people per day, in a city that's generally correlated with test positivity rates of five or 10, or 15% usually means the hospitals are full and stressed and just means a level of risk that if you go into a room of 20 people, there's an almost certain chance that someone in that room is infected. And it's just a very different environment in terms of risk than when you're down to 10.


One of the things I was curious about is that there's the rise of all these rapid antigen tests. Wouldn’t that cause a lot of underreporting? And that might make the 10 cases per 100,000 not as accurate as it used to be?

Dr. Wachter

Absolutely. It's a great question. And I went through this on Twitter, maybe two weeks ago, I said my old number was 10. And it's still 10, and here's why.

I took people through the calculations that basically said, the fact that there are a lot of tests that are positive that don't get ever get reported means that 10 probably is the equivalent of 20, or 30, or 40.

Today, on the other hand, Omicron is substantially milder than the virus was before. If you're fully vaccinated for up to three shots, probably on the order of 80% milder. So I sort of came around to think that thinking those two things kind of cancel each other out.

While we're missing a lot of cases, the implications of a case are substantially milder than they were before, and people have had access to three shots, and those at very high risk, access to either Paxlovid, or a monoclonal antibody, that will lower your risk even more.

And as I calculated each of these things, they sort of cancel each other out. And I ended up in about the same places where I started, which was 10.


Do you think Omicron is going to be the last variant? What if we get a new variant? Do you think your stance on masking or the way you're done all these calculations may change? Let's say the variant is something a bit more serious like Delta?

Dr. Wachter

Well, first question is, will we have a new variant? Anybody who gives you an answer to that is making it up. I think we have absolutely no idea. Because, you know, I mean, people have generally said, there will be variants, of course, there will be billions of variants.

The question is not will there be variants? The question is, will there be a variant that overtakes Omicron as the lead variant, which means it's got to be more infectious or more immune invasive? And then will it be more severe than Omicron?

And I don't think I don't see any way of laying odds on that certainly not zero probability, and certainly not our percent probability. That, you know, I think there's a low but certainly nonzero chance, we will see a variant that is worse than Omicron. If we do, then my behavior will change.

I think there are two ways of thinking about this that to me are wrong. One is we need to keep being careful. Because there might be something that comes out in a month or two. Asking people to continue to be super careful when the environment is one in which things are relatively benign is worse. Most people are going to have already burned out. You will lose credibility when you tell them now you need to become more careful again. So I think that you have to react to the situation now. And the situation now is one that's relatively benign. And to me, merits at least the end of mandates, whether it merits and unmasking is an individual choice.

But I think at the same time, you have to tell people, that there's no way of predicting whether this is the last one. It's possible, we will tell you six months from now that it's time to take out the mask, again, it may be time to have a mandate for you to take out the masks again. Politically, that will be difficult, but it will be the right thing to do if there's a variant.

If there's a variant that comes out that's as bad as Delta and infectious enough that it overtakes Omicron, then there'll be no question in my mind that we've got to go back to a much more hunker down stance than we have today. And that will be entirely appropriate.


There has been a petition going around for the mask mandates to be dropped for children in schools. What do you think about letting kids go without masks? Because we have already let the adults go on mass for slightly over a week by now?

Dr. Wachter

Yeah, I can't see how you defend a stance that says it's okay for adults to be unmasked and go into a bar and go into a gym without a mask on but somehow the kids have to continue to mask — that doesn't make any sense to me.

I think masking mandates for the kids were appropriate when it was appropriate for everyone to be masked. I think if anything, you would argue I would argue that the kids tend on average to have milder illnesses. Not that they never get sick, some of them do, but on average, they have milder illnesses.

The consequences of masking are not as bad as some of the proponents are saying. I mean, it's not the worst thing in the world. But it's probably more significant for a young kid to wear a mask than for an adult to wear a mask.

So, I can't see any real justification to mandate that kids continue to wear and when they when the adults don't.

The state of California just announced today that they're going to remove the mask mandate in a few weeks, which I think is appropriate. There will always be the community argument that people should continue to mask because there are vulnerable people around us. I think that's asking too much of people for them to continue to do something they do not want to do for a small group of vulnerable people who have the means to protect themselves by wearing a good mask, and by getting vaccinated.

And it's imperfect. But I think we've gotten to a point where people do have the means to protect themselves, the tools are out there. And at this point, after two years to say that you have to continue to mask, I just don't know. If that's the answer, then we're going to be saying, you're masking forever.

At some point, you have to say that level of cases is low enough that it's appropriate not to have a mandate. There are vulnerable people, they should continue to protect themselves more.

If you live with them, you probably should continue to protect yourself more, or at least be thoughtful about that. But to say that everyone has to continue to do that because there are some vulnerable people in the community. I can't see that. That doesn't strike me as a sustainable stance.


Thank you that was all very insightful.

Dr. Wachter

Thank you for doing this. Be well.