SARS-CoV-2 Antibody Screening in Healthcare Workers in Non-Infectious Hospitals in Two Different Regions of Southern Poland (Upper Silesia and Opole Voivodeships): A Prospective Cohort Study

Abstract

(1) Background: Detection of asymptomatic or subclinical human coronavirus SARS-CoV-2 infection in healthcare workers (HCWs) is crucial for understanding the overall prevalence of the new coronavirus and its infection potential in public (non-infectious) healthcare units with emergency wards. (2) Methods: We evaluated the host serologic responses, measured with semi-quantitative ELISA tests (IgA, IgG, IgM abs) in sera of 90 individuals in Hospital no. 4 in Bytom, 84 HCWs in the University Hospital in Opole and 25 in a Miasteczko Śląskie local surgery. All volunteers had negative RT-PCR test results or had not had the RT-PCR test performed within 30 days before sampling. The ELISA test was made at two different time points (July/August 2020) with a 2-weeks gap between blood collections to avoid the “serological window” period. (3) Results: The IgG seropositivity of asymptomatic HCWs varied between 1.2% to 10% (Opole vs. Bytom, p < 0.05; all without any symptoms). IgA seropositivity in HCWs was 8.8% in Opole and 7.14% in Bytom. IgM positive levels in HCWs in Opole and Bytom was 1.11% vs. 2.38%, respectively. Individuals with IgA and IgM seropositivity results were observed only in Opole (1.19%). More studies are needed to determine whether these results are generalizable to other populations and geographic as well as socio-demographic locations. (4) Conclusions: 100% of IgG(+) volunteers were free from any symptoms of infection in the 30 days before first or second blood collection and they had no awareness of SARS-CoV-2 infection. Asymptomatic HCWs could spread SARS-CoV-2 infection to other employees and patients. Only regular HCWs RT-PCR testing can reduce the risk of SARS-CoV-2 spreading in a hospital environment. The benefit of combining the detection of specific IgA with that of combined specific IgM/IgG is still uncertain.

The burden of SARS-CoV-2 among healthcare workers across 16 hospitals of Kashmir, India—A seroepidemiological study

“…It is important to know that 25.5% of seropositive HCWs were never tested for infection. Similar results are reported by other studies done on HCWs [27,28]. Asymptomatic individuals also labeled as super spreaders of infection pose a tremendous challenge in the containment of transmission of SARS-CoV-2 infection in the present pandemic in all settings [29].…”

SARS-CoV-2 Seroprevalence in Healthcare Workers before the Vaccination in Poland: Evolution from the First to the Second Pandemic Outbreak

“…The local diversity observed varied between 1.2% and 10% (Opole vs. Bytom, p < 0.05; all without any symptoms). IgA seropositivity in HCWs was 8.8% in Opole and 7.14% in Bytom [ 24 ]. In the study carried out in Poznań (Poland) after the first wave of COVID-19 (July-September 2020), based on the ELISA results, it was found that 1.67% (95%CI 1.13–2.45) had antibodies against SARS-CoV-2 [ 25 ].…”

SARS-CoV-2 antibody screening in healthcare workers: lessons learned from the first months of COVID-19 outbreak in Europe. Significance of serology testing for effective pandemic management and reduction of the occupational risk

“…100.00% of samples were negative; therefore, the diagnostic utility of IgA and IgM antibodies was not confirmed. It is worth noting that in abovementioned study, all positive IgM or IgA sera were collected from asymptomatic HCWs [12]. In other studies, the correlation between IgA serum concentration and severity of SARS-CoV-2 RNA positive was observed.…”

“…On the other hand, Bułdak et al, in their work revealed no statistical significance between positive antibody outcomes and symptoms. To increase the credibility of the outcomes in this research and avoid potential "serological window", the blood was drawn twice [12]. It should be noted that in Bułdak et al's work, reagents were more immunogenic (S1 domain) than in study by Huang et.…”