In lieu of a vaccine or reliable preventative medications, the only approaches currently available to help prevent the spread of COVID-19 are behavioral - handwashing, mask-wearing and social distancing, for example. In a Policy Forum, Johannes Haushofer and Jessica Metcalf argue that it is crucial to identify the "nonpharmaceutical interventions" (NPIs) that most effectively reduce virus transmission at the lowest economic and psychological costs. While handwashing initiatives are relatively inexpensive, sanctioned school and business closures are extremely costly. However, many NPIs are often applied without rigorous evaluation and the approaches to implementing and regulating them are varied, thus making their impact relative to their cost difficult to know. Haushofer and Metcalf discuss how randomized controlled trials (RCTs), compartmental models and spillovers can each be harnessed to evaluate and identify the interventions that work best during a pandemic situation. The authors demonstrate how RCTs can be practically and ethically conducted during a pandemic and used to systematically evaluate the impact of specific intervention strategies, as well as how the effects of NPIs on disease transmission can be estimated using epidemiological compartmental models. What's more, Haushofer and Metcalf suggest that "spillover" effects - or the spread of intervention strategies into non-targeted groups - can be leveraged to increase the overall impact and coverage of NPIs. "If policymakers and scientists combine insights from infection disease epidemiology with carefully and ethically designed impact evaluation, alongside other... methods for studying impact, they will have a powerful tool for reducing the human health, societal and economic costs in the SARS-CoV-2 pandemic," write the authors.