Prevalence of Antibodies to SARS-CoV-2 natural infection and post-vaccination in Irish Hospital Healthcare Workers (PRECISE 2)

Hospital healthcare workers (HCW) are at increased risk of contracting SARS-CoV-2 infection. We aimed to determine the seroprevalence of SARS-CoV-2 antibodies in HCW in Ireland, and to compare the seroprevalence in the same HCW at two points in time. Two tertiary referral hospitals in Irish cities with diverging community incidence and seroprevalence were identified; COVID-19 had been diagnosed in 10.2% and 1.8% of staff respectively by the time of the first cross-sectional study (PRECISE 1, October 2020, during the second wave of the pandemic in Ireland). Community seroprevalence after the first wave of the pandemic was 3.1% and 0.6% respectively. Results of PRECISE 1 showed an overall SARS-CoV-2 seroprevalence of 15% in SJH and 4.1% in UHG, with higher adjusted relative risk (aRR) for male sex, age group 18-29, Asian ethnicity, direct patient contact, role of nurse or healthcare assistant, living with others and living with other HCW (1) (2). This document pertains to the second cross-sectional study (PRECISE 2), which took place six months after PRECISE 1 (in April 2021, during the decline of the third wave of the pandemic in Ireland). By April 2021, occupational health data showed that COVID-19 infection had been diagnosed in 18.5% and 9.2% of staff in SJH and UHG respectively. PRECISE 2 took place four months after the start of vaccination at both sites. The aim of PRECISE 2 was to assess changes in overall seroprevalence with progression of the pandemic, and to further identify HCW risks for seropositivity (demographic, work-related and living arrangements). We also aimed to assess serological response to vaccination in the vaccinated cohort, and to examine changes in individual serostatus over the six-month period between PRECISE 1 and PRECISE 2 for those staff members who participated both times.