Evaluating the effectiveness of social distancing interventions against COVID-19

Laura Matrajt; Tiffany Leung

The term 'flatten the curve', originating from the Centers for Disease Control and Prevention [28] , has been used widely to describe the impact of social distancing interventions. Here, we used a mathematical model to quantify this term by measuring the short-term number of cases, hospitalization, and deaths averted over the first 100 days under four different social distancing interventions and assuming different levels of compliance in the adult population. When looking at the shortterm impact (here considered to be over the first 100 days) of social distancing interventions started early on in the epidemic, our models suggest that only a social distancing intervention involving all the age groups in the population would considerably decrease the number of cases and delay the epidemic the most. However, with as little as 25% reduction in the contact rates in the adult population (combined with 95% in the older adults), one could reduce the number of hospitalizations and deaths by over 90%. Furthermore, reducing the contact rates of adults over 60 alone can have a considerable impact, reducing hospitalizations and deaths by over 30%, in agreement with what others have found [29] . It is important to interpret our results with caution. As any model, we have made important assumptions that could overestimate the effect of the interventions (see limitations below). Quantifying the short-term impact of an intervention is very important since it allows decision makers to estimate the immediate number of resources needed and to plan for further resources in the long term.