A Research Square study of two adjacent North Dakota school districts, one of which mandated student masking and one of which did not, found “no significant difference” in Covid-19 case rates between the two.
The researchers, who received funding from the University of Southern California, noted that “randomized data about the effectiveness of mask mandates in children is still entirely lacking.” Indeed, they wrote, “While observational studies of school mask mandates have had conflicting results, randomized studies have failed to detect an impact of masking on participants under 50 years of age.”
These researchers, however, were fortunate enough to discover “a unique natural experiment to study school-based mask mandates.” Specifically, they analyzed data from two Fargo, North Dakota, school districts: Fargo Public Schools (FPS) and West Fargo Public Schools (WF). Both districts have very similar demographics, although WF has slightly higher percentages of minority and low-income families. Aside from mask mandates, both also had very similar Covid-19 mitigation policies, testing options, and staff vaccination rates, but “FPS had more stringent rules for quarantining close contacts” of Covid-positive students.
The only significant difference between the two districts’ approach to the virus was that at the start of the 2021–2022 school year, FPS required students to be masked throughout the day, while WF did not. On January 17, FPS also made masks optional. This gave researchers an opportunity to compare Covid-19 case rates both when the districts had different policies and when they had the same policies.
“From August 26, 2021, to January 17, 2022, cumulative incidence in the mask[-]compulsory school district [12.9 percent] was almost identical to cumulative incidence in the mask-optional district [13.0 percent],” they found. “Post January 17, 2022, when both districts had mask-optional policies, case rates were also not significantly different,” with FPS having a rate of 5.3 percent and WF having a rate of 5.1 percent.
The researchers observed:
This study found that K-12 school mask mandates were not associated with significantly lower COVID-19 student case rates. This is consistent with adult randomized data on community cloth masking, multiple observational studies of school mask mandates and a systematic review of medical or surgical cloth masking for influenza. Studies of school-based mask mandates are particularly prone to bias as student cases detected within the school may be at least 20x more likely to have been contracted outside of school than in. Other observational studies have reported a negative association between school mask mandates and SARS-CoV-2 cases but may have had important methodological limitations.
While their study wasn’t a randomized trial, it did have significant strengths because of the similarities of the two school districts and the “relatively long study period with data from both the delta and omicron waves” of Covid-19. Moreover, the “partial crossover” when FPS dropped its mask mandate
should have revealed the presence of any major confounding effect. The lack of significant difference between the districts however persisted post partial crossover, when both districts had masks-optional policies. Based on the size of our study and the incidence rate during the study period, we had 80% power to detect a 1.2% difference in incidence between the districts, so if we failed to detect a benefit of mask mandates, that benefit would have been very small.
Of course, if students in either district continued wearing masks once they became optional, this would confound the study, but this does not appear to have been the case. While there is no official data on masking rates in either FPS or WF, “parents and administrators” told the researchers that “masking was near universal in the district with a mask mandate and 5% or less in the masks-optional district.”
“In conclusion,” the researchers wrote, “school mask mandates were not found to be associated with significantly lower student SARS-CoV-2 case rates. This is consistent with a growing body of scientific literature and should be taken into consideration and weighed with the harms and discomfort of masking in the educational setting.”
Unfortunately, the harms caused by most so-called Covid-19 mitigation measures, which those imposing them refused to consider at the time and refuse to admit even at this late date, will be with us for years, if not decades, to come.
