Basic Mitigation Strategies Can Cut COVID-19 Transmission in Schools

By Marilynn Larkin

September 17, 2021

NEW YORK (Reuters Health) - Within-school COVID-19 transmission in North Carolina was significantly limited by the use of basic mitigation strategies such as universal masking, hand-washing and distancing in classrooms, according to a study conducted before the Delta variant of the virus became predominant.

"Vaccination and masking clearly are effective at preventing transmission in schools," Daniel Benjamin of Duke Clinical Research Institute in Durham told Reuters Health by email. "Failure to mask in schools leads to rapid spread. If schools enforce universal masking indoors, most of the within-school transmission in high school is in extracurricular activities, (where) masking and distancing are consistently a challenge."

His team's data collected after the emergence of Delta has been submitted for publication, Dr. Benjamin said. Meanwhile, he noted, aside from universal masking indoors (no 'opting out'), other key mitigation components include vaccinating staff to reduce risk to children and family members of children, vaccinating for extracurricular activities, and eating lunch outside while maintaining distance, because masks will be off.

As reported in Pediatrics, Dr. Benjamin and colleagues investigated secondary SARS-CoV-2 transmission within North Carolina kindergarten through 12th-grade school districts during a winter surge to determine if mitigation strategies could hinder within-school transmission.

The team evaluated data from August 2020 and from October 2020 through February 2021 for more than 100,000 students and staff from 13 school districts that were open for in-person instruction, adhered to basic mitigation strategies, and tracked community- and school-acquired SARS-CoV-2 cases.

A total of 4,969 community-acquired SARS-CoV-2 infections were documented by molecular testing. Through contact tracing, an additional 209 infections were identified among >26,000 school close contacts (secondary attack rate <1%).

Most (75%) within-school transmissions in high schools were linked to school-sponsored sports. School-acquired cases increased slightly during the surge; however, within-school transmission rates remained constant, from presurge to surge, with about one school-acquired case for every 20 primary cases.

The authors state, "In a racially and ethnically diverse real-world setting, with participants strictly adhering to masking and variable distancing, school-acquired SARS-CoV-2 infection was uncommon."

Dr. Margaret Aldrich, Director of Pediatric Infection Control at the Children's Hospital at Montefiore in New York City commented on the study in an email to Reuters Health. "In my experience here in New York, where we had a hybrid model that was similar to that implemented in North Carolina, we did not see increased in-school transmission."

"Universal masking works, especially when combined with improved ventilation and spatial distancing," she said. "I agree with the assertion that 'uncoupling community transmission and school reopening not only is supported by science but also promotes equity.'"

Like Dr. Benjamin, she noted that the study was not done during the Delta surge, which increased transmissibility. Another caveat, she said, is that "the classrooms under study were only at 50% capacity due to the use of the hybrid model."

"On the other hand," she added, "we did not have widespread vaccination at the time of the study, which will greatly mitigate risk of transmission within schools."

"The take home-message has not really changed: universal masking in schools, improved ventilation whenever possible, spatial distancing of at least three feet whenever possible and vaccination for anyone eligible, as that will protect those who are not yet able to get vaccinated," Dr. Aldrich concluded.

SOURCE: Pediatrics, online September 15, 2021