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Study of COVID-19 in Retirement Communities


  • Retirement communities have a greater risk for COVID-19 transmission and severe cases.
  • Abt monitored asymptomatic and symptomatic older adults.
  • Results informed public health guidance and decision-making.
The Challenge

Older adults are among those with the highest risk for medically attended COVID-19. From early in the COVID-19 pandemic, CDC needed data to characterize risk factors and clinical epidemiology of COVID-19 among older adults. The information would inform public health strategies to prevent infection and reduce the burden of severe disease in this population.

The Approach

The COVID-19 Illness and Testing among Retirement Communities in the US (CITRUS) cohort study enrolled retirement community residents from independent living homes and assisted living facilities over a 12-month period. Active surveillance captured symptomatic and asymptomatic COVID-19 cases among participants. The primary objectives of the study were to: 1) estimate the cumulative incidence of asymptomatic and symptomatic infection in community-dwelling older adults; and 2) establish kinetics of immunity over time. Secondary objectives included describing illness severity, infection risk factors, healthcare utilization, and immune response to and effectiveness of vaccination.

The Results

The CITRUS project enrolled 395 participants into the study from participating retirement communities in Florida and followed them prospectively for up to 10 months. Enrolled participants provided respiratory specimens weekly and at acute illness onset during the study period for laboratory confirmation of a COVID infection. They also completed weekly surveys tracking symptoms, exposure risks, and healthcare utilization, and provided blood specimens to assess convalescent and post-vaccination immune responses following a positive PCR test or receipt of vaccine.  

Results are ongoing.