student writing in school classroom with a mask on

National data

In 2021, schools without mask requirements were 3.5 times more likely to have COVID outbreaks than schools with mask requirements.

Link to study:

In this study, 999 schools in Maricopa and Pima counties, Arizona, were analyzed for the prevalence of school-related outbreaks by mask requirements. Out of the 191 school-associated outbreaks that occurred during the study (July 15-August 31, 2021), 59.2% occurred in schools without any mask requirement. Only 8.4% occurred in schools that had a mask requirement in place before school started.  The study accounted for factors that may affect school outbreaks, such as enrollment size, county COVID rates, and school population’s socioeconomic status.

Study conclusion: “Given the high transmissibility of the Delta variant, universal masking, in addition to vaccination of all eligible students, staff members, and faculty and implementation of other prevention measures, remains essential to COVID-19 prevention in K–12 settings.”

Counties with school mask requirements have been associated with smaller increases in pediatric COVID cases than counties without school mask requirements.

Link to study:

Researchers looked at 520 counties starting the 2021-22 school year. Counties either had a mask requirement for all students or for no students. Counties with differing school mask requirements from district to district were excluded. The study measured rates of COVID and accounted for differences that could affect COVID case rates, including age, race and ethnicity, pediatric COVID-19 vaccination rate, COVID-19 community transmission, population density, social vulnerability index score, COVID-19 community vulnerability index score, percentage uninsured, and percentage living in poverty.

Study conclusion: “The results of this analysis indicate that increases in pediatric COVID-19 case rates during the start of the 2021–22 school year were smaller in U.S. counties with school mask requirements than in those without school mask requirements. School mask requirements, in combination with other prevention strategies, including COVID-19 vaccination, are critical to reduce the spread of COVID-19 in schools.”

COVID-19 closures affected nearly 1 million students in August and September 2021.

Link to study:

Researchers searched the internet for school and district closures attributable to COVID. 8,700 school districts were included. 1.5% of schools were affected by COVID-19 school closures, which equaled 933,913 students and 59,846 teachers affected. The number of closures was highest in the South.

Study conclusion: “To prevent COVID-19 outbreaks in schools, CDC recommends multicomponent prevention strategies, including vaccination, universal indoor masking, screening testing, and physical distancing.”

Multilayered prevention strategies were associated with zero camp-based transmission in overnight youth summer camps.

Link to study:

This study assessed the number of COVID-19 cases and potential secondary spread among 7,173 staff members and campers from 50 states, 13 countries, and U.S. military overseas bases at nine independently operated U.S. summer youth camps affiliated with the same organization. The camps implemented multiple prevention strategies including vaccination, testing, podding (cohorting), masking, physical distancing, and hand hygiene during June–August 2021. Vaccination coverage was 93% among eligible persons aged ≥12 years. A total of nine people out of over 7,000 associated with the camp tested positive for COVID via PCR testing. No secondary transmission (transmission from camper to camper) was detected during camp.

Study conclusion: “High vaccination coverage coupled with multiple prevention strategies is critical to averting COVID-19 outbreaks in congregate settings, including overnight camps. These findings highlight important guiding principles for school and youth-based COVID-19 prevention protocols.”

Additional evidence: A group of Louisiana summer camps that mostly did not require masks or vaccines during June–July 2021 experienced 28 camp outbreaks statewide, which included a total of 321 COVID-19 cases, among an estimated 2,988 campers and staff members.

Local data

Children age 0-17 in Dane County have a lower case rate than Wisconsin overall.

Link to data snapshot (see page 3):

Ages 0-11: WI has 1.7 times as many cases than Dane County

Ages 12-15: WI has 2.5 times as many cases than Dane County

Ages 16-17: WI has 2.6 times as many cases than Dane County

As of our 10/28 data snapshot, Dane County has the lowest overall case rate and percent positivity in the state, including among school aged children. Any one factor, like masking, is not the singular cause of this trend. However, these data show that the layered approach in Dane County–including the highest vaccination rates in the state and universal masking in schools—seems to be effective in producing lower case rates among our younger populations than the rest of the state.

Our conclusion: masks and vaccines together are making a difference in school transmission.

We are at a point in the pandemic where we know how to reduce transmission: vaccines, masks, ventilation, and physical distancing. At this point, the biggest factor that determines if we can slow school transmission is how well schools put these tools into action. The CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. That means that no matter what local or state public health orders or guidance/recommendations say for the general public, everyone in schools should be masking up. Vaccines are the most effective tool we have to prevent COVID and reduce severe outcomes, and layering vaccines with other tools like masks and ventilation is the most effective way to prevent school transmission of COVID-19. And both masks and vaccines can create a more consistent learning experience by decreasing the number of students and staff out on quarantine and out sick. We can continue to keep kids healthy and in school by layering prevention strategies together and using prevention strategies consistently.  

This content is free for use with credit to the City of Madison - Public Health Madison & Dane County and a link back to the original post.