SARS-CoV-2 infection in general practice in Ireland: a seroprevalence study

O'Callaghan, Michael E; Ryan, Elizabeth; Walsh, Cathal; Hayes, Peter; Casey, Monica; O'Dwyer, Pat; Culhane, Aidan; Duncan, John W; Harrold, Pat; Healy, Jarlath; Kerin, Emmet; Kelly, Eimear; Hanrahan, Conor; Lane, Ger P; Lynch, Bernie; Meaney, Paraic; O'Connell, Billy; Galvin, Jim; Kennedy, Norelee; Burke, Paul; O'Connell, Nuala H; Dunne, Colum P; Glynn, Liam G

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody testing in community settings may help us better understand the immune response to this virus and, therefore, help guide public health efforts. AIM: To conduct a seroprevalence study of immunoglobulin G (IgG) antibodies in Irish GP clinics. DESIGN & SETTING: Participants were 172 staff and 799 patients from 15 general practices in the Midwest region of Ireland. METHOD: This seroprevalence study utilised two manufacturers’ point-of-care (POC) SARS-CoV-2 immunoglobulin M (IgM)—IgG combined antibody tests, which were offered to patients and staff in general practice from 15 June to 10 July 2020. RESULTS: IgG seroprevalence was 12.6% in patients attending general practice and 11.1% in staff working in general practice, with administrative staff having the lowest seroprevalence at 2.5% and nursing staff having the highest at 17.6%. Previous symptoms suggestive of COVID-19 and history of a polymerase chain reaction (PCR) test were associated with higher seroprevalence. IgG antibodies were detected in approximately 80% of participants who had a previous PCR-confirmed infection. Average length of time between participants’ positive PCR test and positive IgG antibody test was 83 days. CONCLUSION: Patients and healthcare staff in general practice in Ireland had relatively high rates of IgG to SARS-CoV-2 compared with the national average between 15 June and 10 July 2020 (1.7%). Four-fifths of participants with a history of confirmed COVID-19 disease still had detectable antibodies an average of 12 weeks post-infection. While not proof of immunity, SARS-CoV-2 POC testing can be used to estimate IgG seroprevalence in general practice settings.