For the past 2 years, during the pandemic, CGM PI, Brian Skotko, and his multidisciplinary team set up and implemented a randomized control trial to see if they could design a multimodal behavioral intervention that could reduce COVID-19 infection, hospitalization, and death for those persons living in group homes in MA. They focused on people with serious mental illness (SMI) and people with intellectual and/or developmental disabilities (ID/DD)—and the staff who work with them in group homes. This “protocol paper” describes our unique design: a hybrid type 1 effective-implementation cluster randomized trial, which means that half of the 400 participating group homes got our tailored intervention (and the other half continued to receive the statewide recommendations). For the past 2 years, they have been implementing this trial, which has now come to a close.