High prevalence of SARS-CoV-2 antibodies in care homes affected by COVID-19: Prospective cohort study, England

Abstract

Background: We investigated six London care homes experiencing a COVID-19 outbreak and found high rates of SARS-CoV-2 infection among residents and staff. Here we report follow-up investigations including antibody testing in the same care homes five weeks later. Methods: Residents and staff in the initial investigation had a repeat nasal swab for SARS-CoV-2 RT-PCR and a blood test for SARS CoV-2 antibodies using ELISA based on SARS-CoV-2 native viral antigens derived from infected cells and virus neutralisation. Findings: Of the 518 residents and staff in the initial investigation, 186/241 (77.2%) surviving residents and 208/ 254 (81.9%) staff underwent serological testing. Almost all SARS-CoV-2 RT-PCR positive residents and staff were seropositive five weeks later, whether symptomatic (residents 35/35, 100%; staff, 22/22, 100%) or asymptomatic (residents 32/33, 97.0%; staff 21/22, 95.5%). Symptomatic but SARS-CoV-2 RT-PCR negative residents and staff also had high seropositivity rates (residents 23/27, 85.2%; staff 18/21, 85.7%), as did asymptomatic RT-PCR negative individuals (residents 61/91, 67.0%; staff 95/143, 66.4%). Neutralising antibody was detected in 118/ 132 (89.4%) seropositive individuals and was not associated with age or symptoms. Ten residents (10/79 retested, 12.7%) remained RT-PCR positive but with higher RT-PCR cycle threshold values; 7/10 had serological testing and all were seropositive. New infections were detected in three residents and one staff. Interpretation: RT-PCR provides a point prevalence of SARS-CoV-2 infection but significantly underestimates total exposure in outbreak settings. In care homes experiencing large COVID-19 outbreaks, most residents and staff had neutralising SARS-CoV-2 antibodies, which was not associated with age or symptoms.

Disparities of SARS-CoV-2 Nucleoprotein-Specific IgG in Healthcare Workers in East London, UK

“…Robust serological tests have also demonstrated added value in epidemiological investigations for contact tracing, linking clusters of cases retrospectively (40), and determining the prevalence of the infection in high-risk categories such as HCWs or care home residents and staff (41)(42)(43).…”

A case of SARS-CoV-2 reinfection in Ecuador

“…4 The protective immune response to SARSCoV2 infection is not fully understood; however, protection against severe disease has been shown in animal models and inferred in humans infected with the virus. 7 Interestingly, the antibody test performed during the first infection event showed the presence of specific antiSARSCoV2 IgM and no IgG. However, it is not possible using conventional antibody tests to determine whether a protective immune response developed.…”

Incidence of SARS-CoV-2 infection according to baseline antibody status in staff and residents of 100 Long Term Care Facilities (VIVALDI study)

“…Residents of Long-Term Care Facilities (LTCF) that provide residential and/or nursing care to older people have experienced the highest burden of COVID-19 related mortality of any population group. Older adults may exhibit less robust immune responses to infection due to age-related immune-senescence and underlying co-morbidities, and although emerging data suggest most LTCF residents have a detectable immune response following natural infection with SARS-CoV-2, 1–4 the extent to which this protects against a second infection is uncertain. Understanding the degree of protection afforded by prior infection, its duration, and whether primary infection and reinfection differ with regard to disease severity and clinical presentation has major implications for vaccination and for policy decisions regarding the ongoing need or non-pharmaceutical interventions (NPIs) in LTCFs to prevent transmission.…”

“…Most individuals who are infected with SARS-CoV-2 develop antibodies against the spike (S) protein and nucleocapsid (N) at 1-2 weeks following symptom onset, 5 however data from older age-groups and residents of LTCFs are limited by small sample size. 3,4 Neutralising antibodies against the spike protein receptor binding domain (RBD) have been shown to correlate with post-infection immunity, to be dependent on disease severity, 6 and to decline over time, 7 but understanding of the immune correlates of protection against reinfection remains limited.…”