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

Abstract

Background: 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: Conduct a seroprevalence study of IgG antibodies in Irish GP clinics. Design and Setting: Participants were 172 staff and 799 patients of 15 general practices in the Midwest region of Ireland. Methods: This seroprevalence study utilised 2 manufacturers’ point-of-care (POC) SARS-CoV-2 IgM-IgG combined antibody tests, offered to patients and staff in general practice from mid-June to mid-July 2020. Results: Immunoglobulin G (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 SARS-CoV-2 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 to the national average at the time (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.

Potential Application of SARS-CoV-2 Rapid Antigen Diagnostic Tests for the Detection of Infectious Individuals Attending Mass Gatherings – A Simulation Study

“…To estimate prevalence of infectious individuals from reported case incidence data, we assumed that ∼50% of cases were detected. This figure is consistent with the international and national literature (11,(15)(16)(17)(18)(19). Undetected cases are a function of numerous factors including testing capacity, disease incidence, practice regarding referral for testing, and asymptomatic disease.…”

“…Modeling studies have since shown that there was significant under-ascertainment of cases particularly at the peak of the first wave (beginning March 2020 in Ireland) across many countries ( 29 ). Two other Irish sero-prevalence studies have been published: one, conducted in October 2020, found a lower undetected fraction (38%) but was focused on hospital-based healthcare workers ( 18 ) and a second, conducted in June to July 2020, that was based in primary care and found a higher undetected fraction (73%) ( 17 ). For this analysis, a wide range of uncertainty was adopted for the undetected fraction to reflect the limited data available and the fact that the undetected fraction is likely to vary over time.…”

“…Mahajan et al ( 15 ) estimated that 35% of infections were likely detected in the US (data until November 2020) ( 15 ), whereas other studies from Europe estimated figures of 40% ( 11 ) and 52% ( 16 ) from Austria and Italy respectively. In Ireland, three serological studies have been conducted to estimate the proportion of undetected cases, with estimates of the fraction of cases detected ranging from 24 to 56% ( 17 – 19 ). Those studies are typically intended to determine the fraction of the population that have developed antibodies indicating exposure to the disease.…”

Estimated Infection and Vaccine Induced SARS-CoV-2 Seroprevalence in Israel among Adults, January 2020–July 2021

“…We have shown that between January and December 2020, seropositivity rates were between 0.4% (March 2020) and 10.2% (October 2020). During the same year, higher seropositivity rates were observed in New York City (May–July 2020; 18+ years; 23.6% [ 10 ] and June–October 2020; 18+ years; 24.3% [ 11 ]), Saudi-Arabia (May–July 2020; 18+ years; 19.3%) [ 12 ], Ireland (June–July 2020; 18+ years; 12.6%) [ 13 ], and Mexico (August–November 2020; 20–39 (27.9%), 40–59 (27.8%) and 60+ (18.6%) years) [ 14 ]. Similar rates were observed in Ethiopia (June–July 2020; 15+ years, 3.2%) [ 15 ], England (April–September 2020; 18–65 years; 5.9%) [ 16 ], Amsterdam, the Netherlands (June and October 2020; 18–70 years, 9.4%) [ 17 ], Germany (May–June 2020; 18+ years; 11.3%) [ 10 ], and the United States (July 2020 (3.5%), December 2020 (11.5%); 16+ years) [ 18 ].…”