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

Yang, B.; Huang, A. T.; Garcia-Carreras, B.; Hart, W. E.; Staid, A.; Hitchings, M.; Lee, E. C.; Howe, C. J.; Grantz, K. H.; Wesolowski, A.; Lemaitre, J. C.; Rattigan, S. M.; Moreno, C.; Borgert, B. A.; Dale, C. L.; Quigley, N. E.; Cummings, A.; McLorg, A.; LoMonaco, K.; Schlossberg, S.; Barron-Kraus, D. W.; Shrock, H. C.; UFCOVID Interventions Team,; Lessler, J.; Laird, C. D.; Cummings, D. 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 (Reff) 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 an Reff below 1 when combined with either stay at home orders (median Reff 0.97, 95% confidence interval (CI) 0.58-1.39)* or face masks (median Reff 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.