ABSTRACT
Background: We investigated six London care homes experiencing a COVID-19 outbreak and found very 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 involved 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, 208/241 (86.3%) surviving residents and 186/254 (73.2%) staff underwent repeat testing. Almost all SARS-CoV-2 RT-PCR positive residents and staff were also antibody positive five weeks later, whether symptomatic (residents 35/35, 100%; staff, 22/22, 100%) or asymptomatic (residents 32/33, 97.0%; staff 21/22, 95.1%). 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 62/92, 67.3%; staff 95/143, 66.4%). Neutralising antibody was present in 118/132 (89.4%) seropositive individuals and was not associated with age or symptoms. Ten residents (10/108, 9.3%) remained RT-PCR positive but with lower RT-PCR cycle threshold values; all 7 tested 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.Funding: NoneDeclaration of Interests: None.Ethics Approval Statement: The research protocol was approved by the PHE Research Ethics and Governance Group (REGG Ref: NR0204, 07 May 2020).
Subject(s)
COVID-19ABSTRACT
Background: Care homes are experiencing large outbreaks of coronavirus disease 2019 (COVID-19) associated with high case-fatality. We conducted detailed investigations in six London care homes reporting suspected COVID-19 outbreaks during April 2020. Methods: Residents and staff had nasal swabs taken for SARS CoV-2 testing using RT-PCR and were followed-up for 14 days. They were categorized as symptomatic, post-symptomatic or pre-symptomatic if they had symptoms at the time of testing, in the two weeks before or two weeks after testing, respectively, or asymptomatic throughout. Virus isolation and whole genome sequencing (WGS) was also performed. Findings: Across the six care homes, 107/268 (39.9%) residents were SARS CoV-2 positive, including 29 (27.1%) symptomatic, 9 (8.4%) post-symptomatic, 21 (19.6%) pre-symptomatic and 48 (44.9%) who remained asymptomatic. Case-fatality was highest among symptomatic SARS-CoV-2 positive residents (10/29, 34.5%) compared to asymptomatic (2/48, 4.2%), post-symptomatic (2/9, 22.2%) or pre-symptomatic (3/21,14.3%) residents. Among staff, 51/250 (20.4%) were SARS CoV-2 positive and 29/51 (56.9%) remained asymptomatic. RT-PCR cycle threshold s and live virus recovery were similar between symptomatic/asymptomatic residents/staff. WGS identified multiple introductions of different SARS-CoV-2 strains into individual care homes. SARS-CoV-2 strains from residents and staff had identical sequences, as did strains from fatal and non-fatal cases. Interpretation: In care homes reporting a COVID-19 outbreak, a high rate of SARS-CoV-2 positivity was found among residents and staff, half of whom were asymptomatic and are potential reservoirs for on-going transmission. Symptomatic SARS-CoV-2 residents had high case-fatality, while asymptomatic infection was rarely fatal. Symptom-based screening alone is not sufficient for outbreak control.Funding Statement: This study did not receive any funding. The authors are all employed by Public Health England, the study funder, which is a public body — an executive agency of the Department of Health. Declaration of Interests: None.Ethics Approval Statement: PHE has legal permission, provided by Regulation 3 of The Health Service (Control of Patient Information) Regulations 2002, to process patient confidential information for national surveillance of communicable diseases and as such, individual patient consent is not required.
Subject(s)
COVID-19ABSTRACT
Background: We investigated six London care homes experiencing a COVID-19 outbreak and found very high rates of SARS-CoV-2 infection among residents and staff. Here we report follow-up serological analysis in these care homes five weeks later. Methods: Residents and staff had a convalescent blood sample for SARS-CoV-2 antibody levels and neutralising antibodies by SARS-COV-2 RT-PCR five weeks after the primary COVID-19 outbreak investigation. Results: Of the 518 residents and staff in the initial investigation, 208/241 (86.3%) surviving residents and 186/254 (73.2%) staff underwent serological testing. Almost all SARS-CoV-2 RT-PCR positive residents and staff were antibody positive five weeks later, whether symptomatic (residents 35/35, 100%; staff, 22/22, 100%) or asymptomatic (residents 32/33, 97.0%; staff 21/22, 95.1%). 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 62/92, 67.3%; staff 95/143, 66.4%). Neutralising antibody was present in 118/132 (89.4%) seropositive individuals and was not associated with age or symptoms. Ten residents (10/108, 9.3%) remained RT-PCR positive, but with lower RT-PCR cycle threshold values; all 7 tested were seropositive. New infections were detected in three residents and one staff member. Conclusions: RT-PCR testing for SARS-CoV-2 significantly underestimates the true extent of an outbreak in institutional settings. Elderly frail residents and younger healthier staff were equally able to mount robust and neutralizing antibody responses to SARS-CoV-2. More than two-thirds of residents and staff members had detectable antibodies against SARS-CoV-2 irrespective of their nasal swab RT-PCR positivity or symptoms status.