Global infection and mortality rates from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are disproportionately high in certain populations, including amongst older people. Care home residents are frequently exposed to infection due to contact with staff and other residents, and are highly susceptible to infection due to their age and co-morbidity. In England, official statistics suggest that at least 25% of all deaths in care home residents since the start of pandemic are linked to coronavirus disease 2019 (COVID-19), but limited testing for SARS-CoV-2 early in the pandemic means estimates of the true burden of disease are lacking. Additionally, little is known about patterns of transmission between care homes, the community and hospitals, or the relationship between infection and immunity in care home staff and residents. The VIVALDI study plans to address these questions. VIVALDI is a prospective cohort study aiming to recruit 6,500 staff and 5000 residents from 105 care homes across England. Successive rounds of testing for infection will be performed over a period of 12 months. Nasopharyngeal swabs will detect evidence of viral RNA and therefore active infection (accompanied by collection of data on symptoms), whereas blood tests will detect antibodies and evidence of cellular immunity to SARS-CoV-2. Whole genome sequencing of viral isolates to investigate pathways of transmission of infection is planned in collaboration with the COVID-19 Genomics UK Consortium. Qualitative interviews with care home staff will investigate the impact of the pandemic on ways of working and how test results influence infection control practices and behaviours. Data from residents and staff will be linked to national datasets on hospital admissions, antibody and PCR test results, mortality and care home characteristics. Data generated will support national public health efforts to prevent transmission of COVID-19 and protect care home staff and residents from infection. Protocol registration: ISRCTN14447421 05/06/2020