Prevalence of Antibodies to SARS-CoV-2 Following Natural Infection and Vaccination in Irish Hospital Healthcare Workers: Changing Epidemiology as the Pandemic Progresses

Abstract

BackgroundIn October 2020 SARS-CoV-2 seroprevalence among hospital healthcare workers (HCW) of two Irish hospitals was 15 and 4. 1%, respectively. We compare seroprevalence in the same HCW population 6 months later, assess changes in risk factors for seropositivity with progression of the pandemic and serological response to vaccination.MethodsAll staff of both hospitals (N = 9,038) were invited to participate in an online questionnaire and SARS-CoV-2 antibody testing in April 2021. We measured anti-nucleocapsid and anti-spike antibodies. Frequencies and percentages for positive SARS-CoV-2 antibodies were calculated and adjusted relative risks for participant characteristics were calculated using multivariable regression analysis.ResultsFive thousand and eighty-five HCW participated. Seroprevalence increased to 21 and 13%, respectively; 26% of infections were previously undiagnosed. Black ethnicity (aRR 1.7, 95% CI 1.3–2.2, p < 0.001), lower level of education (aRR 1.4 for secondary level education, 95% CI 1.1–1.8, p = 0.002), living with other HCW (aRR 1.2, 95% CI 1.0–1.4, p = 0.007) were significantly associated with seropositivity. Having direct patient contact also carried a significant risk being a healthcare assistant (aRR 1.8, 95% CI 1.3–2.3, p < 0.001), being a nurse (aRR 1.4, 95% CI 1.0–1.8, p = 0.022), daily contact with COVID-19 patients (aRR 1.4, 95% CI 1.1–1.7, p = 0.002), daily contact with patients without suspected or confirmed COVID-19 (aRR 1.3, 95% CI 1.1–1.5, p = 0.013). Breakthrough infection occurred in 23/4,111(0.6%) of fully vaccinated participants; all had anti-S antibodies.ConclusionThe increase in seroprevalence reflects the magnitude of the third wave of the pandemic in Ireland. Genomic sequencing is needed to apportion risk to the workplace vs. the household/community. Concerted efforts are needed to mitigate risk factors due to ethnicity and lower level of education, even at this stage of the pandemic. The undiagnosed and breakthrough infections call for ongoing infection prevention and control measures and testing of HCW in the setting of close contact. Vaccinated HCW with confirmed infection should be actively assessed, including SARS-CoV-2 whole genome sequencing (WGS), serology testing and assessment of host determinants, to advance understanding of the reasons for breakthrough infection.

Cumulative incidence, prevalence, seroconversion, and associated factors for SARS-CoV-2 infection among healthcare workers of a University Hospital in Bogotá, Colombia

“…We found that HCWs aged ≥35 years had a lower risk of SARS-CoV-2 infection than those aged <35 years, probably due to higher concern regarding possible unfavorable outcomes of infection leading to higher compliance with preventive measures in that age group [ 27 , 28 ]. A similar trend has been reported in some studies [ 10 , 29 , 30 ], whereas other suggest older ages are more likely to be infected [ 11 , 31 ].…”

Risk factors for SARS-CoV-2 infection in healthcare workers following an identified nosocomial COVID-19 exposure during waves 1–3 of the pandemic in Ireland

“…Male sex has been identified as a risk factor in HCWs for SARS-CoV-2 seropositivity in a number of studies [ 2 , 16 , 17 ] with quoted odds ratios ranging from 1.39 to 3.21. The Prevalence of COVID-19 in Irish Healthcare Workers Study, an independent multicentre seroprevalence study of anti-SARS-CoV-2 antibodies in HCWs in Ireland, which included the current study site, found an increased risk of SARS-CoV-2 seropositivity in male HCWs with an aRR 1.2 (95% CI 1.0–1.4, P = 0.016) [ 13 ]. Studies have demonstrated heterogeneous immune responses to SARS-CoV-2 infection in men and women, including delayed peaks in anti-SARS-CoV-2 immunoglobulins in men [ 18 , 19 ], however these findings generally are inconclusive and lack statistical analysis to relate these findings to infectivity or disease severity [ 20 ].…”

“…Variability in SARS-CoV-2 infection by job role has been demonstrated in a number of studies, with nursing staff and HCAs [ 5 , 6 , 13 , 14 , 30 ] often cited as being at increased risk of infection. In our findings, no individual job role was determined to have consistently increased risk of infection following a given in-work COVID-19 exposure.…”

Identification of severe acute respiratory syndrome coronavirus 2 breakthrough infections by anti-nucleocapsid antibody among fully vaccinated non-healthcare workers during the transition from the delta to omicron wave

“…Using anti-N antibody to identify BTIs, Laing et al reported a BTI rate of 0.88% for symptomatic infection and 25% for asymptomatic infection in 227 healthcare workers ( 21 ). Others reported BTI rates of 0.6 and 0.8% among 4111 and 130 fully vaccinated healthcare workers, respectively ( 35 , 36 ). Another study reported a BTI rate of 4.6 and 5.3% in patients with immune-mediated inflammatory diseases with ( n = 3207) and without immunosuppressants ( n = 985), respectively, and 4.0% in 822 healthy controls ( 37 ).…”