CDC School Guidance Affirmed in Study Backing Masks, Airflow

(Bloomberg) -- Mask use and improved ventilation were linked to a lower rate of Covid-19 cases in schools in a study that reinforced federal health guidance on how to keep the nation’s children safe.

Among Georgia elementary schools, the frequency of Covid cases at the end of last year was 37% lower in schools that required teachers and staff to use masks, according to a Friday report by the U.S. Centers for Disease Control and Prevention. The incidence of Covid cases was 39% lower in schools that enhanced ventilation.

Even as the CDC relaxed recommended precautions for fully vaccinated people, it has recommended schools maintain universal mask use until the end of the current school year. The agency has not yet released guidance for the next school year, but the study provides data that could help shape upcoming recommendations. CDC will update its guidance for schools in the coming weeks, it said in a statement.

Until vaccines are available for children less than 12 years old, “universal and correct mask use is a critical prevention strategy CDC recommends that schools prioritize regardless of vaccination status for in-person learning,” according to the report.

States have been adjusting their policies around Covid restrictions, with Texas Governor Greg Abbott banning public schools from mandating masks after June 4 as part of an executive order issued this week.

The data comes as health authorities in the U.S. and globally recognize the risk the virus can spread through the air. Scientists have long argued the virus is airborne and are calling for ventilation systems to be overhauled. But the CDC and the World Health Organization have been criticized for being slow to the scientific evidence around airborne transmission.

The study found schools that used dilution methods alone -- including opening windows, openings doors or using fans -- saw a 35% lower incidence of cases. Schools that used both dilution methods and air filters saw a 48% lower incidence.

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