Contact Tracing Policy for Masked Students May be an Important Confounding Variable

The recent article by Boutzoukas et al¹  analyzed the association of universal vs partial vs optional school masking policies with secondary in-school infection and found an unexpectedly strong association between masking policies and secondary infections given recent studies.^2,3  Unfortunately, it appears the authors have failed to consider at least 1 critically important confounding variable. The Centers for Disease Control and Prevention (CDC)⁴  state that “the close contact definition excludes students who were between 3 to 6 feet of an infected student if both the infected student and the exposed student(s) correctly and consistently wore well-fitting masks the entire time.” We are aware of numerous districts across the country where contact tracing during the period of the study¹  would not have correctly identified coronavirus disease 2019 cases truly transmitted in the school to have come from the school because a masked student transmitting to another...