Seroprevalence study of SARS-CoV-2 antibodies in healthcare workers following the first wave of the COVID-19 pandemic in a tertiary-level hospital in the south of Ireland

Objective This study investigated seroprevalence of SARS-CoV-2-specific IgG antibodies, using the Abbott antinucleocapsid IgG chemiluminescent microparticle immunoassay (CMIA) assay, in five prespecified healthcare worker (HCW) subgroups following the first wave of the COVID-19 pandemic. Setting An 800-bed tertiary-level teaching hospital in the south of Ireland. Participants Serum was collected for anti-SARS-CoV-2 nucleocapsid IgG using the Abbott ARCHITECT SARS-CoV-2 IgG CMIA qualitative assay, as per the manufacturer's specifications. The groups were as follows: (1) HCWs who had real-time PCR (RT-PCR) confirmed COVID-19 infection (>1-month postpositive RT-PCR); (2) HCWs identified as close contacts of persons with COVID-19 infection and who subsequently developed symptoms (virus not detected by RT-PCR on oropharyngeal/nasopharyngeal swab); (3) HCWs identified as close contacts of COVID-19 cases and who remained asymptomatic (not screened by RT-PCR); (4) HCWs not included in the aforementioned groups working in areas determined as high-risk clinical areas; and (5) HCWs not included in the aforementioned groups working in areas determined as low-risk clinical areas. Results Six of 404 (1.49%) HCWs not previously diagnosed with SARS-CoV-2 infection (groups 2-5) were seropositive for SARS-CoV-2 at the time of recruitment into the study. Out of the 99 participants in group 1, 72 had detectable IgG to SARS-CoV-2 on laboratory testing (73%). Antibody positivity correlated with shorter length of time between RT-PCR positivity and antibody testing. Quantification cycle value on RT-PCR was not found to be correlated with antibody positivity. Conclusions Seroprevalence of SARS-CoV-2 antibodies in HCWs who had not previously tested RT-PCR positive for COVID-19 was low compared with similar studies.