The Study to Investigate COVID-19 Infection in People Living in Ireland (SCOPI): A seroprevalence study, June to July 2020

Background: Robust data on SARS-CoV-2 population seroprevalence supplement surveillance data in providing evidence for public health action. Aim: To conduct a SARS-CoV-2 population-based seroprevalence survey in Ireland. Methods: Using a cross-sectional study design, we selected population samples from individuals aged 12-69 years in counties Dublin and Sligo using the Health Service Executive Primary Care Reimbursement Service database as a sampling frame. Samples were selected with probability proportional to the general population age-sex distribution, and by simple random sampling within age-sex strata. Antibodies to SARS-CoV-2 were detected using the Abbott Architect SARS-CoV-2 IgG Assay and confirmed using the Wantai Assay. We estimated the population SARS-CoV-2 seroprevalence weighted for age, sex and geographic area. Results: Participation rates were 30% (913/3,043) and 44% (820/1,863) in Dublin and Sligo. Thirty-three specimens had detectable SARS-CoV-2 antibodies (1.9%). We estimated weighted seroprevalences of 3.12% (95% confidence interval (CI): 2.05-4.53) and 0.58% (95% CI: 0.18- 1.38) for Dublin and Sligo, and 1.69% (95% CI: 1.13- 2.41) nationally. This equates to an estimated 59,482 (95% CI: 39,772-85,176) people aged 12-69 years nationally having had infection with SARS-CoV-2, 3.0 (95% CI: 2.0-4.3) times higher than confirmed notifications. Ten participants reported a previous laboratory-confirmed SARS-CoV-2-infection; eight of these were antibody-positive. Twenty-five antibody-positive participants had not reported previous laboratory confirmed infection. Conclusion: The majority of people in Ireland are unlikely to have been infected with SARS-CoV-2 by June-July 2020. Non-pharmaceutical public health measures remained key pending widespread availability of vaccination, and effective treatments.