Effect of specific non-pharmaceutical intervention policies on SARS-CoV-2 transmission in the counties of the United States

Yang, Bingyi; Huang, Angkana T.; Garcia-Carreras, Bernardo; Hart, William E.; Staid, Andrea; Hitchings, Matt D. T.; Lee, Elizabeth C.; Howe, Chanelle J.; Grantz, Kyra H.; Wesolowksi, Amy; Lemaitre, Joseph Chadi; Rattigan, Susan; Moreno, Carlos; Borgert, Brooke A.; Dale, Celeste; Quigley, Nicole; Cummings, Andrew; McLorg, Alizée; LoMonaco, Kaelene; Schlossberg, Sarah; Barron-Kraus, Drew; Shrock, Harrison; Lessler, Justin; Laird, Carl D.; Cummings, Derek A. T.

Non-pharmaceutical interventions (NPIs) remain the only widely available tool for controlling the ongoing SARS-CoV-2 pandemic. We estimated weekly values of the effective basic reproductive number (R(eff)) using a mechanistic metapopulation model and associated these with county-level characteristics and NPIs in the United States (US). Interventions that included school and leisure activities closure and nursing home visiting bans were all associated with a median R(eff) below 1 when combined with either stay at home orders (median R(eff) 0.97, 95% confidence interval (CI) 0.58–1.39) or face masks (median R(eff) 0.97, 95% CI 0.58–1.39). While direct causal effects of interventions remain unclear, our results suggest that relaxation of some NPIs will need to be counterbalanced by continuation and/or implementation of others.