Modeling serological testing to inform relaxation of social distancing for COVID-19 control

Background While social distancing efforts have been successful at slowing the spread of SARS-CoV- 2, these measures cannot be sustained indefinitely. In this paper, we examine how serological testing can reduce the risk of relaxing social distancing measures while also providing a way for test-positive individuals to return to more normal levels of activity. Methods We use an SEIR-like compartmental model that accounts for serological test status to examine if widespread serological testing can reduce the adverse effects of relaxing social distancing measures, in terms of total deaths and health system burden. In our model, social distancing measures are relaxed to a greater extent for those who test positive compared to those who have not been tested or test negative, allowing a return to work and partial restoration of other social contacts to pre-pandemic levels. All individuals preferentially interact with those who have tested positive, such that seropositive individuals act as immunological ‘shields.’ We consider a range of potential testing capacities and the implications of an imperfect test for this strategy. Results Although relaxing social distancing interventions increases total deaths, serologic testing as a part of this strategy can reduce population risk. If social distancing restrictions are relaxed by 50% in tandem with monthly serological testing of the general United States (US) population, 174,000 deaths would be averted and 67% of the US population would be released from social distancing after 1 year, as compared to a scenario without serological testing. Sustaining moderate levels of social distancing can help to flatten the epidemic curve, reducing health system burden below the US critical care capacity. Implications Modeling studies suggest that serological testing can be used to relax social distancing measures preferentially for seropositive individuals, insofar as antibodies can be established as a correlate of protection against SARS-CoV-2 infection. Implementing a strategy of serological testing and shielding can reduce population risk while offsetting the severe social and economic costs of a sustained shutdown.