For the study, the researchers analyzed rates of SARS-CoV-2 infections between October 2020 and February 2021 among more than 2,000 nursing home residents (median age 86) and staff. Antibody testing was used to determine whether they'd had a previous infection up to 10 months earlier. Residents with a previous infection were 85% less likely to be infected during the four-month study period than those who had never been infected, while staff with past infections were 60% less likely to be infected than staff who had never been infected…