Evaluating the effectiveness of social distancing interventions against COVID-19

Laura Matrajt; Tiffany Leung

For this part of the analysis, we consider the effects of social distancing interventions over the first 100 days of the epidemic and assume that the social distancing interventions started on day 50. This corresponds to the approximate date where social distancing interventions started in Washington state. To investigate the sensitivity of the model to the parameters chosen, we ran 1,000 simulations (as described in the Methods). We obtained curves that varied widely over both the number of cases and the duration and timing of the epidemic (figures S1, S2, S3). We show here results of simulations done with the mean values (R 0 = 2.26, an infectious period lasting 5 days and a latent period of 5.1 days). We report cases as well as the proportion of cases, hospitalizations and deaths averted during the first 100 days. While reducing the contacts of adults over 60 only averts only a moderate number of cases (21%, Figure 3 ; and 57% for the adults over 60, Figure S4 )), the number of hospitalizations and deaths are reduced by 36% and 47% respectively for the whole population (Figure 4) , and by 56% for the adults over 60 yo ( Figure S5 ). Adding a social distancing intervention in children drastically slows down the epidemic curve ( Figure 3 ). Further, hospitalizations and deaths are reduced by 75 and 80% respectively, with the reductions evenly distributed across all age groups ( Figures S5 and S6) .