New data analyzed and published by the ABC Science Collaborative sheds new light on school safety during a COVID-19 surge and reinforces the message that masking is an effective strategy to mitigate within-school transmission.

The new study, which was published recently in Pediatrics (updated September 2021), includes over 100,000 students and staff from 13 school districts that were open for in-person instruction between October 26, 2020 and February 28, 2021 and implementing mitigation measures such as masking. Researchers from the ABC Science Collaborative compared this data, which was collected during a “winter surge” of COVID-19 cases, with data from August 2020 to determine how the rise in community cases impacted in-school transmission.

During the winter surge timeframe, 4,969 community-acquired cases of COVID-19 were recorded. After contact tracing in partnership with local health department staff, an additional 209 cases of in-school transmission were recorded. The majority of within-school transmission in high schools occurred within school-sponsored sports.

These results align closely with initial findings from the ABC Science Collaborative, which were also published in Pediatrics and included data collected pre-winter surge, during the first quarter schools were open for in-person instruction (from August 15, 2020 to October 23, 2020).

“Although we did see a slight increase in school-acquired cases during the winter surge, the within-school transmission rate remained very low at less than 1 percent,” said Kanecia Zimmerman, MD, MPH, co-chair of the ABC Science Collaborative. “Another way to say this is that for every 20 cases we saw come in from outside the school, we had only one case within the school. Although this data was collected before the rise of the Delta variant, these findings are especially timely as we are experiencing another surge in cases and underscore the importance of masking as schools re-open for the fall semester.”

These data are also consistent with findings released in an ABC Science Collaborative report, which documented a very low within-school transmission rate across 100 school districts in North Carolina.

“Prior to this study, we didn’t have any solid data on how a rise in community cases would impact the amount of COVID-19 we were seeing within school walls,” said Danny Benjamin, MD, PhD, MPH, co-chair of the ABC Science Collaborative. “Now, these data confirm that mitigation measures, particularly masking, are quite effective in limiting the spread of COVID-19. As pediatricians and public health experts, we also encourage vaccination whenever possible as the ultimate mitigation measure. For example, we recommend that schools link vaccination to participation in high school sports, where we are seeing higher rates of transmission.”

These data were published in the wake of new CDC guidance that recommends masking for all individuals in K-12 schools regardless of COVID-19 vaccination status.