MZb oversaw laboratory work. hazards models were used to estimate protective effectiveness of previous exposure. SARS-CoV-2 spike, nucleoprotein, and neutralising antibodies were assessed at multiple timepoints as part of Rauwolscine the longitudinal follow-up. == Findings == Between April Rabbit polyclonal to AKR1D1 10 and Aug 3, 2020, we recruited and tested 1625 individuals (933 staff and 692 residents). 248 participants were lost to follow-up (123 staff and 125 residents) and 1377 participants were included in the follow-up period to Jan 31, 2021 (810 staff and 567 residents). There were 23 reinfections (ten confirmed, eight probable, five possible) in 656 previously infected individuals (366 staff and 290 residents), compared with 165 primary infections in 721 susceptible individuals (444 staff and 277 residents). Those with confirmed reinfections had no or low neutralising antibody concentration before reinfection, with boosting of titres after reinfection. Kinetics of binding and neutralising antibodies were similar in older residents and younger staff. == Interpretation == SARS-CoV-2 reinfections were rare in older residents and younger staff. Protection from SARS-CoV-2 was sustained for longer than 9 months, including against the alpha variant. Reinfection was associated with no or low neutralising antibody before reinfection, but significant boosting occurred on reinfection. == Funding == Public Health England. == Introduction == The COVID-19 pandemic had a disproportionately high effect on care homes worldwide, with case fatality rates of up to 25% among the oldest and most frail residents.1,2,3,4Care home staff, although younger and healthier than Rauwolscine residents, have among the highest SARS-CoV-2 infection and fatality rates of any occupation.5Consequently, residents and staff in long-term care facilities are prioritised for COVID-19 vaccination in many countries.6,7Understanding immune responses and duration of protection after infection in this high-risk group, particularly in the context of new variants, is crucial for designing vaccination strategies.8Highly transmissible alpha and delta variants have successively replaced early strains in the UK and elsewhere, and other variants such as beta and gamma that have less clear transmission advantages but more pronounced antigenic variation circulate in other parts of the world. We investigated COVID-19 outbreaks in care homes in England early in the pandemic and found high rates of SARS-CoV-2 infection among residents and staff.2We did a prospective longitudinal cohort of 13 London care homes in April, 2020, with regular sampling of staff and residents, including serum antibodies.9Antibody seroprevalence varied markedly between care homes (from 107840%), indicating marked heterogeneity of exposure during the first wave (peak in April, 2020).10118 (894%) of 132 seropositive individuals had neutralising antibodies irrespective of age, sex, or symptom status.11 == Research in context. == Evidence before this study We searched PubMed with the terms COVID-19 or SARS-CoV-2, care home, nursing home, nursing facility or residential home, and reinfection or humoral immunity to identify publications relating to SARS-CoV-2 reinfections and longevity of antibody responses to natural infection between Jan 1, 2020, and June 30, 2021. Protection from reinfection following natural infection was reported to last at least 6 months in healthy adults, mainly in longitudinal cohorts of health-care workers. Among older care Rauwolscine home residents and staff, reports suggest protection for at least 10 months after primary infection. Added value of this study Antibody persistence was similar between care home residents and staff members, with reinfections occurring rarely in either group, indicating high protection for at least 9 months after previous infection, including against emerging SARS-CoV-2 variants. The few individuals with reinfection had low or undetectable neutralising antibody titres before reinfection. Implications of all the available evidence Given the high morbidity and mortality associated with COVID-19 outbreaks in care homes, our data provide evidence of high antibody persistence in older residents after primary infection.