1,2; Erica E. Smith3; Tabatha Offutt-Powell3; Rick Hong3; Delaware Case Investigation and Contact Tracing Teams3; Thu-Ha Dinh2; Eric Pevzner2 (View author affiliations)COVID-19 mitigation measures (e.g., stay-at-home orders and public mask mandate) and fundamental public health interventions (e.g., case investigations and contact tracing with prompt isolation or quarantine) are primary approaches to preventing and controlling SARS-CoV-2 community transmission.State-mandated stay-at-home orders and public mask mandates coupled with case investigations with contact tracing contributed to an 82% reduction in COVID-19 incidence, 88% reduction in hospitalizations, and 100% reduction in mortality in Delaware during late April–June.The combination.