COVID-19 Illness and Testing among Retirement Communities in the US (CITRUS) Cohort Study

Project: Research project

Project Details


Coronavirus disease 2019 (COVID-19) is a disease caused by the emergent and rapidly spreading severe acute respiratory syndrome coronavirus (SARS-CoV-2) [1]. The World Health Organization declared the COVID-19 outbreak a global pandemic on March 11, 2020 [2]. Many questions about COVID-19 urgently need to be answered, including knowledge gaps regarding infection and re-infection rates, illness characterization, risk and protective factors, differences between symptomatic and asymptomatic infections, and efficacy of interventions and vaccination when they become available. During the global public health emergency brought about by a new coronavirus, tools and infrastructure available to fill these critical gaps in knowledge and practice must be developed and implemented as quickly as possible.
Older adults are among those with the highest risk for medically attended COVID-19. Characterization of risk factors and clinical epidemiology of COVID-19 among older adults may inform public health strategies to prevent infection and reduce the burden of severe disease in this population. Because older adults are particularly vulnerable to severe disease once infected with SARS-CoV-2 virus and may be prioritized for a pandemic vaccine once it is available, this population is a high priority for early studies of the incidence and characterization of SARS-CoV-2 infection and COVID-19 illness. In addition, immune response among older adults and especially frail adults may be reduced compared to younger individuals, including more rapid waning of antibodies following infection or vaccination. A protocol unique to this population is therefore needed to obtain early and critical information about incidence of infection and illness, characterization of illness, and immune response to infection.
Our primary objectives for this current proposal, the COVID-19 Illness and Testing among Retirement Communities in the US (CITRUS) study, are to: 1) estimate the cumulative incidence of asymptomatic and symptomatic infection in community-dwelling older adults in the US; and 2) establish kinetics of immunity over time. Secondary objectives include describing illness severity, risk factors for infection, healthcare utilization, and immune response to vaccination and vaccine effectiveness when SARS-CoV-2 vaccines become available.
We will enroll approximately 1,500-2,000 participants within 3 months. Sampling of eligible participants will occur from individuals residing in independent living/assisted living facilities or residing in the community and receiving centralized care through one of the participating continuing care retirement communities (CCRCs). The initial study period will be 6 months, with an option to continue data collection for an additional year. Participants enrolled in our cohort will provide respiratory and/or mucosal specimens weekly and at acute illness onset during the study period. Those specimens will be shipped to and analyzed by an approved CDC-contracted central laboratory. Participants will also complete weekly surveys tracking general health, symptoms, exposure risks, and healthcare utilization for those with symptoms or confirmed disease. Participants will provide blood specimens at study enrollment, at quarterly intervals, and as needed to assess convalescent and post-vaccination immune responses such as serum antibody levels following a positive PCR test or receipt of vaccine. Antibody testing will be performed at the CDC or designated laboratory using CDC-approved assays. Recruitment, enrollment, consent, weekly survey, and participant testing data will be collected and stored utilizing REDCap. CDC and NIH best practices will be followed for recruitment, consent, data management, and data sharing. An optional second year will provide for monitoring of the durability of immune response over a longer time period and continued evaluation of vaccine response.
Effective start/end date2/1/212/2/21


  • HHS: Centers for Disease Control and Prevention (CDC): $117,499.00