COVID-19 serology in nursing homes and long-term care facilities: prevalence of seroconversion in the Amiens-Picardie University Hospital.

Since December 2019, an emerging infectious viral disease triggered by SARS-CoV-2 has caused a global pandemic. Elderly people, being more fragile, are the most affected by the severity and lethality of this disease. The residential care facility for dependent elderly people (Ehpad) and the long-term care facilities at the Amiens University Hospital registered their first COVID-19 cases in February 2020, which lead to the opening of a dedicated COVID-19 unit and aspecific protocol for isolation. This descriptive study analysed the prevalence of COVID-19 seroconversion within the Ehpad and the long-term care facilities at the Amiens University Hospital. Both this screening test and the nasopharyngeal swab PCRs were used to assess the impact of the COVID-19 epidemic on the residents of the Ehpad and the long-term care facilities. On 15 and 16 June 2020, the serological tests for COVID-19 were positive for 146 (66.1%) of the residents tested. The seroconversion rate was significantly different (p < 0.001) between the Ehpad (88.7%) and the long-term care facility (45.6%). During the epidemic, there was no excess mortality index within the Ehpad and the long-term care facility services of the Amiens University Hospital. Among frail patients, the role of immunosenescence can be evoked to account for the absence of this inflammatory reaction. This study showed that isolating the infected patient in a dedicated unit significantly reduces the risk of seroconversion and contamination compared to isolating them within their own unit.