Multiple scientific studies suggest that masking can help limit transmission of SARS-CoV-2 in schools, contrary to claim in Federalist article

It’s back to school season in the U.S. and with rising COVID-19 case numbers, including among children too young to receive the COVID-19 vaccines, American schools have become battlegrounds over disagreements about preventative measures. Many of these disputes focus on whether masks should be mandatory or optional for children; in some cases, these disagreements have escalated to physical altercations, disorderly conduct and threats from parents who don’t believe masks should be required.

Among American politicians, Florida governor Ron DeSantis is one of the more vocal critics of mask mandates. In an executive order signed on 30 July 2021, two of the reasons given by DeSantis to prohibit mask mandates in schools and “ensuring parent’s freedom to choose – masks in schools”, are (a) that “studies have shown that children are at a low risk of contracting a serious illness due to COVID-19” and (b) that the U.S. Center for Disease Control and Prevention’s (CDC) recent guidance on universal masking in schools “lacks a well-grounded scientific justification”.

An article in The Federalist from 24 August 2021 by Shawn Fleetwood recently addressed a CDC study on masking in schools, and crowed that the study “vindicates Florida Republican Gov. Ron DeSantis” because it showed that there is “no science behind masks on kids”.

As we’ll show below, it is inaccurate to claim there is no science behind the use of masks for children, especially considering the surge in COVID-19 cases currently occurring in the U.S.

Claim 1 (Inaccurate): “No science behind masks on kids”

Critics of mask mandates in schools often claim there is a lack of scientific evidence to support the CDC’s recommendation. In his executive order, DeSantis said that the CDC guidance “lacks a well-grounded scientific justification”. PolitiFact fact-checked this claim, and found it to be false (see here). Speaking to PolitiFact, Lynn Goldman, the dean of the Milken Institute of Public Health at George Washington University, said that “what the science actually shows is that for children ages two and above, masks are not only protective but needed”.

The Federalist article cited a specific CDC study that looked at mask use and ventilation in elementary schools in Georgia (kindergarten through grade 5) between November and December 2020 to support this claim^[1]. This study found that the incidence of COVID-19 was 37% lower in schools that require teachers and staff to wear masks and 39% lower in schools that improved ventilation.

Because a little over half of the schools also required students to wear masks, the study also investigated whether there was a difference in the incidence of COVID-19 between schools where masks were required and schools where masks were optional. The study found that the incidence of COVID-19 was 21% lower in schools with required masking, but this result wasn’t statistically significant compared to schools where mask use was optional.

Statistical significance is a method for evaluating whether a result of an experiment was due to chance or if it’s a real result. In the case of required vs. optional masking in schools, if the 21% lower incidence of COVID-19 had reached statistical significance, one could be confident that the result was due to the mask requirement; since statistical significance was not reached, we can’t be confident the result wasn’t due to chance.

For The Federalist, the lack of statistical significance appeared to vindicate DeSantis, “who has been a vocal opponent of the policy due to its lack of scientific evidence”. However, the Georgia school study isn’t the only study to look at the effect of masking requirements in schools. In a science brief on COVID-19 transmission in schools, the CDC stated that “most studies that have shown success in limiting transmission in schools have required that staff only or staff and students wear masks as one of the school’s prevention strategies”. The CDC listed six studies in the science brief,^[2-7]. A seventh study done in Florida primary and secondary schools that looked at factors associated with student case rates of COVID-19, found that schools without mask mandates had higher student case rates^[8].

One study cited by the CDC involved 11 North Carolina schools, representing over 90,000 students and staff, and they found low transmission of SARS-CoV-2 in schools, despite the study occurring during a time (August to October 2020) when community transmission was high^[2]. Students were required to wear masks, and other prevention strategies, including routine hand-washing and daily temperature checks among others, were adopted.

When asked about how to reduce the transmission of COVID-19 in schools, Kanecia Zimmerman, the first author of the North Carolina study and a professor of pediatrics at Duke University, told Duke Today that:

“There are two effective ways to do that. 1: Vaccination. 2: Masking. In the setting of schools […] the science suggests masking can be extremely effective, particularly for those who can’t get vaccinated while COVID-19 is still circulating”.

Claim 2 (Lacks context): Children are at a low risk of contracting a serious illness due to COVID-19

Compared to adults, the risk of serious illness and death in children is very low. According to the American Academy of Pediatrics (AAP) and the Children’s Hospital Association, as of 19 August 2021, over 4.59 million children (14.6% of all cases) have tested positive for COVID-19 in the U.S. since the beginning of the pandemic. According to the Centers for Disease Control and Prevention (CDC), as of 18 August 2021, 430 children (0 to 18; 0.07% of all COVID-19 deaths) have died of COVID-19 in the U.S.

This low risk is the basis for many arguments that measures adopted to keep adults safe from COVID-19, such as staying at home and wearing masks, provide few benefits for children and are therefore unnecessary, including DeSantis’ executive order.

However, as Debbie-Ann Shirley, a pediatric infectious diseases specialist at University of Virginia (UVA) Health in Charlottesville, told Science News, “anything that kills more than 350 children a year is going to automatically rank in the top 10 causes”. Later in the same Science News piece, Taison Bell, a critical care and infectious disease doctor at UVA Health’s medical intensive care unit, provided a comparison: “think about if 300 children had died over the past year from lightning strikes or from shark attacks […] We would be doing things a lot differently when it came to going to the beach or being outside when it was raining”.

Moreover, the low risk of serious illness and COVID-19 deaths isn’t equally distributed within the U.S. Even though pediatric COVID-19 cases tend to match the country’s demographics, children of color are more likely to get severely ill and die of COVID-19 compared to White children. Hispanic or Latino children account for over 36% and Black children account for 22% of COVID-19 deaths, despite representing only 18.5% and 13.4%, of the U.S. population, respectively.

Currently, pediatric COVID-19 cases and hospitalizations in the U.S. are rising sharply. An NBC News analysis of data released by the Department of Health and Human Services found that on 18 August 2021 an average of more than 1,200 children a day are in U.S. hospitals for COVID-19. To put that number in perspective, that’s four times the number of hospitalized children in early July 2021.

Given the increase in COVID-19 cases in the U.S. and the Delta variant, which is more contagious, the CDC now “recommends universal indoor masking by all students (age two and older), staff, teachers, and visitors to K-12 schools, regardless of vaccination status”. The AAP had previously made the same recommendation in July 2021. Both the CDC and the AAP stressed the importance of layering prevention strategies, also known as the Swiss Cheese Pandemic Defense. This involves a combination of different protective measures, such as masks and physical distancing, to make in-person learning safe.

Figure 1. Virologist Ian Mackay created this graphic illustration showing how combining multiple, imperfect measures provides the greatest protection against the spread of COVID-19.

Claim 3 (Inaccurate): Masks are detrimental to the health of children

Though not addressed in The Federalist article, DeSantis’ executive order also claimed that “making children may lead to negative health and societal ramifications”, and that “forcing children to wear masks could inhibit breathing, lead to the collection of dangerous impurities including bacteria, parasites, fungi, and other contaminants, and adversely affect communications in the classroom and student performance”.

DeSantis is not the only one to claim that masks are detrimental to the health of children. In an op-ed in the Wall Street Journal published on 8 August 2021, surgical oncologist Marty Makary and pediatrician H. Cody Meissner listed a few other concerns including fogged glasses, severe acne caused by masks, and “increased levels of carbon dioxide in the blood”.

PolitiFact recently did a thorough breakdown of the claims about the health detriments of masks for children made by DeSantis and members of his office, concluding that masks are largely safe for children.

Among the most common claims is that masks are dangerous because they lead to oxygen deficiency and increased levels of carbon dioxide in the blood; this was previously debunked by many fact-checking organizations, including Health Feedback (see here and here). In summary, both carbon dioxide and oxygen molecules are far smaller than the filter size of face masks, allowing them to pass easily through masks, even N95s. However, this isn’t the case for the virus SARS-CoV-2, which travels via droplets that get caught by the masks’ fabric. Health Feedback previously addressed how masks form a barrier for respiratory droplets (see here).

Another claim about face masks is that pathogens like bacteria and fungi can accumulate on them. Claims that masks wearing cause bacterial infections were also fact-checked multiple times; in a Reuters fact-check, a team from the Meedan Digital Health Lab made up of global health scientists and infection preventionists said that “there was ‘no evidence’ to suggest face masks can increase the chance of developing pneumonia, ‘or any other bacterial, fungal or viral infection in the lungs’”.

Johns Hopkins University pediatric infectious diseases specialist Matthew Thomas debunked many claims about face masks in a 22 July 2020 post from Johns Hopkins All Children’s Hospital’s Newsroom. On the topic of mold buildup on cloth masks, Thomas said that “clean, dry masks will not develop mold or make you sick” and that proper daily laundering of face masks “removes any viruses, bacteria or respiratory secretions that may build up on the mask”.

Disposing or properly washing one’s mask after use can also help prevent “maskne” (a portmanteau of the words “mask” and “acne”). As for how to keep glasses from fogging, there are a number of solutions, but the best one is to use a well-fitting mask.

As for whether face masks can impact communication in schools and student performance, experts told PolitiFact that this is more plausible. In an opinion piece for Scientific American, David Lewkowicz, a scientist at Yale University who studies perceptual and cognitive development in infants and young children, wrote that masks may impact speech and language development because babies lip-read and use it as a visual speech cue. However, Lewkowicz also wrote that caregivers can compensate for this by following CDC guidelines when outside, but engaging in a lot of unmasked communication with babies when at home.

In September 2020, when the New York Times asked scientists who study how children use cues that masks might hinder, whether masks might impact development, all mentioned the ability of children to adapt to masks and find ways to communicate. Moreover, as Eva Chen, a developmental psychologist at Hong Kong University of Science and Technology, told the New York Times, there is no evidence “that children from cultures with much more extensive face covering are any worse at recognizing faces or emotions”.

In summary, while masks may impact communication, scientific evidence suggests that masks are safe for children. As the AAP, which recommends universal school masking, put it:

“Face masks can be safely worn by all children 2 years of age and older, including the vast majority of children with underlying health conditions, with rare exception. Children 2 years of age and older have demonstrated their ability to wear a face mask”.

Conclusion

Despite claims that masking children doesn’t work and masks aren’t necessary for children, the science suggests the opposite. Evidence shows that masks are largely safe for children two years of age and older and that universal masking can limit the transmission of SARS-CoV-2 in schools.

REFERENCES

• 1 – Gettings et al. (2021) Mask Use and Ventilation Improvements to Reduce COVID-19 Incidence in Elementary Schools — Georgia, November 16–December 11, 2020. Morbidity and Mortality Weekly Report.
• 2 – Zimmerman et al. (2021) Incidence and Secondary Transmission of SARS-CoV-2 Infections in Schools. Pediatrics.
• 3 – Gandini et al. (2021) A cross-sectional and prospective cohort study of the role of schools in the SARS-CoV-2 second wave in Italy. The Lancet Regional Health Europe.
• 4 – Fricchione et al. (2021)  Data-Driven Reopening of Urban Public Education Through Chicago’s Tracking of COVID-19 School Transmission. Journal of Public Health Management and Practice.
• 5 – Link-Gelles et al. (2021) Limited Secondary Transmission of SARS-CoV-2 in Child Care Programs – Rhode Island, June 1-July 31, 2020. Morbidity and Mortality Weekly Report.
• 6 – Kim et al. (2021) Characteristics of COVID-19 Cases and Outbreaks at Child Care Facilities – District of Columbia, July-December 2020. Morbidity and Mortality Weekly Report.
• 7 – Volpp et al. (2021) Minimal SARS-CoV-2 Transmission After Implementation of a Comprehensive Mitigation Strategy at a School – New Jersey, August 20-November 27, 2020. Morbidity and Mortality Weekly Report.
• 8 – Doyle et al. (2021) COVID-19 in Primary and Secondary School Settings During the First Semester of School Reopening — Florida, August–December 2020. Morbidity and Mortality Weekly Report.