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Brian Lehrer: Brian Lehrer on WNYC. Students, teachers and school staff are settling into the new school year with the cloud of the Delta variant hanging over their heads. Here in New York and elsewhere, the approach to keeping schools open for the sake of the students is one of multiple layers of protection, vaccines for those old enough to get them, ventilation, social distancing, and of course, masks.

The New York State Department of Health mandates mask wearing for all K-12 public and private school students, though a federal lawsuit is challenging this mandate. For the moment, it's been held up.

My next guests are clear, "Universal masking in schools can save lives." These are their words in a guest essay in the New York Times that maybe some of you saw with the headline We Studied One Million Students. This Is What We Learned About Masking.

With me now are the authors of this op-ed and the report on masking referenced in that New York Times piece, Danny Benjamin and Kanecia Zimmerman professors of pediatrics at Duke University, and co-chairs of the ABC Science Collaborative which pairs scientists and physicians with school and community leaders to help them understand the most current and relevant data about COVID-19. Dr. Zimmerman, Dr. Benjamin, thanks for doing this. Welcome to WNYC.

Danny Benjamin: Thank you.

Kanecia Zimmerman: Thanks.

Brian Lehrer: Dr. Benjamin, who are these 1 million students you studied?

Danny Benjamin: We're one of about now 10 publications from around the United States, three have come from Duke University, and seven others from about a half a dozen other states that show consistently the same thing, that masking is effective to prevent within school transmission or school acquired COVID infection. As a reminder, infections will occur in the community.

When they occur in the community, people will come to school with infections, but the deliverable for schools is to prevent within school infections, or kids and adults getting infected as a result of being in school. Last spring, the school districts of North Carolina were required by state law to report all of their COVID data to us at Duke and University of North Carolina. We had over a million children and adults in face-to-face instruction in the spring of 2021 in North Carolina.

The school districts reported to us all the cases where children and adults acquired the infection outside of school and the using contact tracing and some testing, they differentiated with the health department infections that were acquired at school. It turns out with the ancestral variant, and with the Alpha variant of COVID-19, the within school transmission rate was about 1%.

It was less than 1% in North Carolina, and that's consistent with our prior work in the fall and it's consistent with the seven or eight other publications out there from around the country.

Brian Lehrer: Dr. Zimmerman, did you have a control group or a contrasting group that was more unmasked, and they had different transmission rates among the kids?

Kanecia Zimmerman: In North Carolina, there was a mask mandate just as there is currently in New York, so there wasn't a control group in the setting of North Carolina. However, as we have seen from other places across the world, particularly the UK, where in some places they haven't used masking as a strategy, the secondary attack rate of the number of people who come into close contact with someone who comes into the building who's infected, the secondary attack rate there is about 10%.

There's also been reports from places like Israel, been reports from places like Florida, where they weren't necessarily masking and the secondary attack rate ranged anywhere from 10% to about 30%. We are hopeful this year or we will this year actually be able to collect information from districts who are masked and unmasked in a natural experiment that is happening here in the United States.

We have an ongoing data collection effort to be able to evaluate that more carefully but what we have so far is data from other places outside of North Carolina.

Brian Lehrer: Now, listeners, we can take your questions on mask wearing in schools for Dr. Danny Benjamin and Dr. Kanecia Zimmerman, professors of Pediatrics at Duke and co-chairs of the ABC Science Collaborative, a Duke initiative that pairs scientists and doctors with schools and other community organizations and helps them understand the most recent and relevant COVID-19 data. 646-435-7280, 646-435-7280, with your masks in schools questions, or tweet @BrianLehrer.

We'll watch our Twitter go by for good questions too. Dr. Zimmerman, is there anything on fit, or the type of masks, or the quality of masks? There's so many articles we could find about how you can't just slap a cloth mask on your face and think you're protected, you have to do some kind of a fit test to see that you're not leaking air really. I guess also the air can't leak in, because those droplets and other particles are so small, or that different materials matter. Did you look at that at all?

Kanecia Zimmerman: Sure. What we know about mask policies is that just because if you have a mask policy in place, doesn't mean people are actually masking appropriately. Which is one of the things that you're actually bringing up. Certainly having masks that cover your nose, your mouth, and your chin without gaping holes in it is going to be much more effective, but remember that my mask protects you and your mask protects me.

In the context of the information that we gathered throughout the fall, the winter, and even with the 1 million children here in North Carolina, people were wearing a variety of types of masks. Many children, many, many children were wearing cloth masks, some were wearing surgical masks, very, very few were wearing things like KN95s, N95s, mostly teachers if people were going to wear them.

What we have found is that what you wear or wearing something is better than wearing nothing. Wearing something that you can wear consistently so that's more likely to be something like a cloth mask or more likely to be something like a surgical mask rather than a KN95 or N95 mask. Consistency actually matters as well as the way that things are fit.

There are a number of ways that we can make things that better.

You can double mask as the CDC has found. There are also ways to manipulate your masks so that the ear loops are actually adjustable for children and there are masks that are smaller size for children too. Thinking about those things actually is very, very important, but wearing something, wearing it consistently is the most important thing here.

Brian Lehrer: David in the Hudson Valley, you're on WNYC. Hi, David.

David: Hey, Brian, thanks for taking my call. This is David Zweig. I'm a journalist. I wrote a large piece for New York Magazine about masking children in schools. I just wanted to ask the authors of the Duke study how they can claim that their study in particular found that masks work when there was no control group. There was a mask mandate everywhere, so they had no one to compare to. There were no schools or students without a mask mandate to compare to.

Brian Lehrer: Dr. Benjamin.

Danny Benjamin: Brian, this is Danny. I think this is a great question that we see over and over again. There's three aspects to this question. Number one is Dr. Zimmerman already covered for you. Number two, I would refer the listener to the Marin County, California data that just came out in the MMWR. In that setting, one unmasked teacher was able to infect 26 other people in Marin County, California despite having air purifier in place, doors and windows open across the classroom.

This particular classroom had two walls worth of windows. It was in California on a peninsula like setting. The students and the teacher were distanced more than six feet apart. The third thing that we have-- so we have external control groups. We don't have an internal control group. The third thing that we have is this summer, we've had data collection ongoing in and outside the state of North Carolina.

The mask mandate was in place in North Carolina with the Delta variant and the secondary attack rate remained very low on the order of 1%-2%. We had several school districts this late August that tried to go to the unmasked environment, as Dr. Zimmerman said, the voluntary masking and the secondary attack right there is 10-30 fold higher.

In fact, we had three school districts from which we have data from August of 2020 to August of 2021 where they had both the ancestral variant and the Delta variant, and their secondary attack rate was about 1%. They went two weeks in a voluntary mask situation. In the seven school days that they went voluntary masking, they had more within school transmission in those seven days than they had in the prior 52 weeks combined. They have since gone back to face mask and face coverings and they have now settled back into their anticipated and very, very solid, very, very low secondary attack rate. This is a fantastic question by the listener.

It's one that we get commonly, and it's one that as Dr. Zimmerman mentioned, our current collaboration that is now nationwide and any school district in the country can participate in for free. We are asking school districts from throughout the country to send their data to Duke.

Brian Lehrer: David, I'm curious for you as somebody who did write that long article in New York Magazine if you're convinced by that answer. That there's enough naturally occurring control group data from other places that seem to indicate pretty conclusively, the effectiveness of masks on kids.

David: From everything I've read, the evidence is very mixed and without knowing what their trajectory was of cases in the surrounding community in any of those places, it's hard to know. There was a correlation where oftentimes the same areas that maybe are having less mitigation measures in schools, maybe in communities that already have a higher rate, for example. One thing that I find most persuasive is looking at Europe.

We have tens of millions of children throughout Europe who are not wearing masks in schools. There's no evidence I'm aware of that shows that children in Europe are at a higher risk of severe illness or other bad consequences than they are in America. Even though all of these different countries in Europe have a wide variety of ranges of vaccination, a range of case rates, and a range of mortality rates per capita. It's all over the map so to speak, yet have the one unifying feature is none of them are masking young child.

Brian Lehrer: David, thank you for your call. One of you referred to Europe as a comparative control group because they are having more cases among children. Do I remember that correctly? Who said that?

Kanecia Zimmerman: That was me. The secondary attack rates in some of the data from the spring in Europe has been reported [inaudible 00:12:35] upwards of 10% in those settings. Also remember that Europe has a pretty robust-- and at least this was the UK, pretty robust screening testing program and that people were getting screening testing twice per week. Thinking about they certainly have a higher tolerance for what the secondary attack rate would be.

Here in North Carolina, it is for sure that a secondary attack rate of about 10% would be fairly concerning when we have tolerated about 1%-3%.

Brian Lehrer: Dr. Zimmerman, this is off the topic of your study, but I wonder if studying these kinds of things you might have a reaction to a story here in New York City. Right now, one school so far in the new school year has had to shut down completely because of a COVID outbreak. It's P.S. 79 on the east side of Manhattan, where 22 staff members tested positive for COVID.

The kids were masked, I believe, and no child outbreaks, but 22 staff members and according to the New York City schools chancellor, it began with a single unvaccinated adult in a group setting. I'm just curious if you've seen this story or even from the little that I just told you if you think there's a lesson there or something that's consistent with outbreaks that you've come across in your research.

Kanecia Zimmerman: Sure. That's an excellent question. We certainly know that in the setting-- I think Danny mentioned this from Marin County, California, where a single unvaccinated teacher who came to school symptomatic, had no masking in place as she was reading to her children, and 26 other people became infected. We're seeing a similar story in New York as you just mentioned.

We certainly know that adults can efficiently spread the virus. We certainly know that the reproductive number for the Delta variant is higher than what the ancestral variants have been. We know that in the setting of outbreaks, the outbreaks have the potential to be larger. Thinking about mitigation strategies in place, I think it's telling that there were no outbreaks among the kids who were consistently masked.

I think we really need to think about this as we move forward and putting policies into place that would make sure that teachers are protected and that they are vaccinated and that can help us with decreasing the risk of outbreaks, particularly coming from that particular source.

Brian Lehrer: Sophie in Sleepy Hollow. You're on WNYC. Hi, Sophie.

Sophie: Hi. Yes, I'm calling because I have an almost one-year-old. I gave birth last October in the middle of all of the lockdown stuff. She's in daycare and-

Brian Lehrer: Congratulations.

Sophie: Oh, thanks. She's been in daycare for a few months and I am of course very worried about schools going back and older kids wearing masks, not wearing masks, but I'm finding very little information or anyone really talking about babies and infants, and how if they're contracting COVID in daycares. If there's any studies on how many babies are getting COVID. If it's very serious.

They obviously can't wear masks. Really, all I'm hearing is for a parent with a baby under two, it's your best [inaudible 00:16:10] is to be safe [inaudible 00:16:12].

Brian Lehrer: Dr. Zimmerman, have anything on that for Sophie? I do note that in the New York City school system, for example, if I remember correctly, the kindergarteners and the pre-K students don't have to mask, it starts in first grade, but Sophie is asking about babies-- Oh, I'm being corrected right now on that they do have to mask. I don't know where I got that, so I stand corrected, but the caller is asking really about babies under two.

Kanecia Zimmerman: Sure. Some of the earliest data from the pandemic, even before we had information about K-12 schools, we did have some information about childcare centers. What we learned from that particular situation is that when there were policies and procedures that were in place where the adults were masking, at the time obviously vaccination wasn't an option.

When adults were staying home if they were ill, then they had situations in which they did not spread and were able to kind of operate appropriately. We know that in situations where people weren't doing that, where adults were coming to work and they were unmasked that, again, there was a problem with people spreading to the children, and then even some of the children, babies, spreading to adults.

We do know that younger kids are less efficient in spreading Coronavirus than adults and older children actually are. We are unfortunately, however, seeing that there are two peaks of where we are seeing severe disease and that is in those 0-4 years of age and in the teenagers now that we have a Delta variant, now that we're seeing increasing cases.

Certainly thinking about strategies to protect the adults and that making sure the adults are protecting the children, particularly in the situations under age of two where they can't mask is going to be really, really important.

Brian Lehrer: What I remembered wrong by the way, just to clarify, is that the pre-K kids and the kindergarten kids in New York City don't have to get tested. They don't have to participate in the weekly testing regimen that's just been imposed. They do have to mask. Then somebody just wrote in that in their son's preschool, the Department of Health just changed it, and even the two-year-olds and three-year-olds have to mask in daycare settings.

For two-year-olds and three-year-olds during the first week of the school year, most of the two-year-olds were not masked. I guess, Dr. Benjamin, there's that line that parents like Sophie have to navigate-- and of course she's got an infant, but at what age do you start masking?

Danny Benjamin: Well, it's clear that the two, three, and four-year-olds are fully capable of masking. In fact, in North Carolina schools, we've done a mask monitoring study where we've had school leadership walk through the buildings and assess what fraction of the population is masked at random times covering 10% of each building with each walkthrough. We can show that masking compliance is greater than 90%.

We can show that age does not predict masking compliance, but rather adult leadership predicts masking compliance. Now under age four, and certainly the younger the kids get, the more encouragement is needed to get mask compliance going, and the more supportive encouragement is needed. This is where Dr. Zimmerman's point about the comfort of the mask really comes on line for the two, three, and four-year-olds. Really, in the first weeks of having masking in a preschool, you're going to see reduced compliance, but you'll be able to get that up into very, very high target ranges for these children. They are capable of doing it. In fact, most of our masking problems relate to the adults, not to the toddlers.

Brian Lehrer: This is WNYC FM HD and AM New York, WNJT-FM 88.1 Trenton, WNJP 88.5 Sussex, WNJY 89.3 Netcong, and WNJO 90.3 Toms River. We are New York and New Jersey public radio with just a few minutes left with Dr. Danny Benjamin and Dr. Kanecia Zimmerman, professors of pediatrics at Duke University. They studied the effects of masking on Coronavirus spread in 1 million children.

Before you go, we need to touch the other side of this because maybe you were just mentioning COVID spread, but what a lot of the opponents of mask mandates for children in schools argue is you can't just look at that. You have to look at the price that they might pay in terms of social and emotional learning and measure that somehow. Dr. Zimmerman, was that in this study or have you looked at it in other contexts?

Kanecia Zimmerman: We didn't look at it in this particular study but there have recently been some more qualitative studies that have started to come out and we are in the process of actually having qualitative data coming out here from North Carolina. Where our researchers are asking children what their thoughts are, what their thoughts are about going back to school, what their thoughts are about masking, what their thoughts are about being concerned about all of these things.

At least, the preliminary data that we've seen suggests that children want to be back in school. They want to be back safely. If masking gets them there, they are okay with doing it. I can tell you from my own personal experiences, my children, they don't care anything about their masks. They just want to be able to do the things that they were doing before and are happy to wear the mask if it gets them there.

Brian Lehrer: I know you would get called so, Dr. Benjamin, if you want to pick up on this from parents who say, "Yes, I've heard that as a generalization, but my kid hates it."

Danny Benjamin: Sure. Children take their cues from adults. If adults have great angst about whether or not their children are wearing mask, then their children are much more likely to share that same angst. The second point about this is that when we have been looking in schools where the parents in some of the rural North Carolina school districts are very, very much against masking, but the kids, once they cross the schoolhouse door, they keep their mask on to a rate 90% or greater.

They do so relatively drama-free. The reports that we've gotten from the school districts where there's a lot of anti-mask sentiment and a lot of communities in North Carolina, but the school leadership reports to us that the angst that is shared is shared largely by the adults.

Brian Lehrer: Last thing, I'm just curious, the mask mandate in New York City, Dr. Benjamin, also applies to recess and other outdoor activities that take place during school hours. Are they all that necessary outside?

Danny Benjamin: What we've started to do is we characterize school districts as risk-averse and risk-tolerant. For the risk-tolerant districts, these tend to be in more rural areas. We know that they are very, very unlikely to mask during recess. For the risk-averse areas, which tend to be more urban school districts, they tend to really want to do everything that they can right now during this month.

We tell them, "Look, if you really want to do everything that you can to minimize COVID, then masking during recess is a reasonable thing." Because research-- Brian, when you and I were growing up, that was eight kids playing kickball. Now, it's eight kids clustered on a picnic table looking at an iPhone. For the more rural or risk-tolerant school districts, really getting them on board with masking indoors, that gets you 80% or 90% of the way there.

We don't talk very much about the masking outside except as an option. If they are seeing more COVID transmission in their schools than they would like to see, then we encourage them to up-regulate their mitigation strategies and outdoors masking is an option.

Brian Lehrer: That makes it sound like maybe start without outdoor masking and see if they're okay?

Danny Benjamin: I think for a risk-tolerant school district, yes, that's what I like to see. We have plenty of risk-averse districts in North Carolina and throughout the country where they say, "Look, we want to stay on top of the ball. We want to get on control of this from the get-go. We want to get off to a very, very strong solid start. We want to be able to pull mitigation strategies off rather than have to add them later." We support both approaches as reasonable.

Brian Lehrer: I'm going to throw in one other Twitter comment that came in here and ask you, Dr. Zimmerman, how you deal with things like this because I'm sure you get it a lot? Listener tweeting as "Mom, New York City" or retweeting somebody else who first tweeted it.

I see as angry Brooklyn mom wrote, "Listening to Brian Lehrer and I want to scream into the void. I don't know who the guests are, but they are insisting that two-year-olds can mask just fine. Unbelievable. I can't believe this is our country." Do you hear that a lot?

Kanecia Zimmerman: We hear it some but the proof really is in the observation of what's happening. We certainly have colleagues who have two-year-olds, who have three years and four-year-olds who have taught their children how to mask appropriately. Again, it may take time. It may take some reinforcement, but we certainly have observed people doing this successfully.

Not all two-year-olds may be able to do this, but we certainly have observed this in two-year-olds doing successfully. The AAP recommendations currently are ages two and up for masking.

Brian Lehrer: Dr. Zimmerman, Dr. Benjamin from Duke University pediatrics, thank you both very much for your time today. We really appreciate it.

Danny Benjamin: Thank you.

Kanecia Zimmerman: Thank you.

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