An outbreak of coronavirus disease began in a large penitentiary complex in Brazil on April 1, 2020. By June 12, there were 1,057 confirmed cases among inmates and staff. Nine patients were hospitalized, and 3 died. Mean serial interval was ≈2.5 days; reproduction number range was 1.0–2.3.

Objectives To assess SARS-CoV-2 prevalence and health outcomes among inmates over 60 years of age during a COVID-19 outbreak in a major penitentiary complex in the Federal District, Brazil. Methods A mass test campaign was performed on May 13, 2020, with the use of antibody-detection rapid tests for asymptomatic inmates and RT-PCR for symptomatic. Those with negative results were retested on June 16. Inmates were interviewed for the characterization of background health conditions and the presence of symptoms. Results A total of 159 inmates were evaluated. In the first mass testing, we found that 79.9% (127/159) had been infected and 53.5% (68/127) of those reported symptoms. There were 17 new cases after the second testing, meaning 90.6% (144/159) of inmates had some positive result. Comorbidities were present in 67.3%; two hospitalizations and no COVID-related deaths were recorded. Conclusion More than 90% of inmates over the age of 60 were infected with SARS-CoV-2 during the outbreak. Periodic health monitoring, active case finding and early care for symptomatic patients were the main actions that contributed to positive post-infection outcomes. Such measures must be considered as essential components for the surveillance of COVID-19 in environments with limited capacity to promote social distance, such as penitentiary institutions.