A systematic review of studies of mask mandates for children, published Saturday in the British Medical Journal's Archives of Disease in Childhood, found "No association" with infection or transmission in 16 of the 22 observational studies and "Critical" or "Serious" risk of bias in the six countervailing studies.
Self-reported SARS-CoV-2 infection was higher the more often people said they wore masks, according to a Norwegian study accepted for publication Nov. 13 in the Cambridge University Press journal Epidemiology and Infection.
One of them, UCSF's Tracy Beth Hoeg, is known for a 2021 study for the Centers for Disease Control and Prevention that found lower COVID infection rates in schools than the surrounding community.
"Masking recommendations appear to be entirely based on mechanistic and observational data," they wrote, noting that a much broader systematic review of mask RCTs by the research collaborative Cochrane concluded masks make "Little to no difference" against flu or COVID. The six studies that found lower infection with mandates, or a negative association, were "Potentially confounded by crucial differences between masked and unmasked groups," such as how many days students were in school, size of schools, testing and contact-tracing policies and "Baseline differences in case rates in all phases of the pandemic."
A Boston-area study that received glowing media coverage despite widespread criticisms of its methodology, for example, "Failed to find the same association when expanding the population to include the entire state or using different statistical analysis and also found the initial study's results were likely confounded by differences in prior infection rates."
"Recommendations to wear face masks in the community are largely informed by low certainty evidence from observational studies," the paper concluded.
"More randomized trials or quasi-experimental studies are needed to improve our insights" on masks and respiratory infections.
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