Effectiveness of 3 Versus 6 ft of Physical Distancing for Controlling Spread of Coronavirus Disease 2019 Among Primary and Secondary Students and Staff: A Retrospective, Statewide Cohort Study

Background. National and international guidelines differ about the optimal physical distancing between students for prevention of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission; studies directly comparing the impact of >= 3 versus >= 6 ft of physical distancing policies in school settings are lacking. Thus, our objective was to compare incident cases of SARS-CoV-2 in students and staff in Massachusetts public schools among districts with different physical distancing requirements. State guidance mandates masking for all school staff and for students in grades 2 and higher; the majority of districts required universal masking. Methods. Community incidence rates of SARS-CoV-2, SARS-CoV-2 cases among students in grades K-12 and staff participating in-person learning, and district infection control plans were linked. Incidence rate ratios (IRRs) for students and staff members in traditional public school districts with >= 3 versus >= 6 ft of physical distancing were estimated using log-binomial regression; models adjusted for community incidence are also reported. Results. Among 251 eligible school districts, 537 336 students and 99 390 staff attended in-person instruction during the 16-week study period, representing 6 400 175 student learning weeks and 1 342 574 staff learning weeks. Student case rates were similar in the 242 districts with >= 3 versus >= 6 ft of physical distancing between students (IRR, 0.891; 95% confidence interval, .594-1.335); results were similar after adjustment for community incidence (adjusted IRR, 0.904; .616-1.325). Cases among school staff in districts with >= 3 versus >= 6 ft of physical distancing were also similar (IRR, 1.015, 95% confidence interval, .754-1.365). Conclusions. Lower physical distancing requirements can be adopted in school settings with masking mandates without negatively affecting student or staff safety.