The Effects of Nonpharmaceutical Interventions on COVID-19 Cases, Hospitalizations, and Mortality: A Systematic Literature Review and Meta-analysis

INTRODUCTION: This review aimed to assess the effects of various nonpharmaceutical interventions on cases, hospitalizations, and mortality during the first wave of the COVID-19 pandemic. METHODS: To empirically investigate the impacts of different nonpharmaceutical interventions on COVID-19–related health outcomes, a systematic literature review was conducted. The effects of 10 nonpharmaceutical interventions on cases, hospitalizations, and mortality across 3 periodic lags (2, 3, and ≥4 weeks after implementation) were studied. Articles measuring the impact of nonpharmaceutical interventions were sourced from 3 databases by May 10, 2022, and risk of bias was assessed using the Newcastle-Ottawa scale. RESULTS: Across the 44 papers, the authors found that policy stringency corresponded to decreased per capita mortality across all lags (–0.13, –0.24, and –0.24 per 100,000, respectively). Masks were associated with mitigative effects on both cases (–2.76 per 100,000) and deaths (–0.19 per 100,000), whereas restaurant closures and travel restrictions corresponded to decreased mortality. Shelter-in-place orders suggested later impacts (after 2 weeks) on cases (–2.9 per 100,000). Although limited gatherings and school and business closures corresponded to reduced per capita mortality in 2 or 3 weeks, or both, their impacts diminished after 4 weeks. The 3 nonpharmaceutical interventions studied in hospitalizations showed negative estimates. DISCUSSION: When assessing the impact of nonpharmaceutical interventions, considering the duration of effectiveness after implementation has paramount significance. Although some nonpharmaceutical interventions may reduce the COVID-19 impact, others can disrupt the mitigative progression of containing the virus after 3 weeks. Policymakers should be aware of both the scale of their effectiveness and duration of impact when adopting these measures for future COVID-19 waves.