SARS-CoV-2 seroprevalence among workers in a hospital in Madrid

Abstract

Background: The impact of the first wave of the pandemic due to SARS-CoV-2 has been enormous in Spanish hospitals; being Madrid one of the most affected communities. The aim of this study was to analyze the impact of the pandemic on the workers of a hospital located in one of the most affected areas of Madrid (Alcalá de Henares) using a chemiluminescence immunoassay (CLIA).

Methods: We conducted a seroprevalence survey between June 25th and July 31st; 2020; over hospital workers from our institution. This study population was previously analyzed using a diagnostic approach which consisted of PCR and a serologic rapid test. For the present survey; prevalence of IgG antibodies against SARS-CoV-2 was studied using chemiluminescence. We analyzed the prevalence in healthcare workers (HCW) and non-healthcare workers (nHCW). Information about professional category; use of personal protective equipment (PPEs) and previous COVID-19 contacts was collected to determine the risk factors associated with SARS-CoV-2 seropositivity. Comparisons were made using the Mann-Whitney U test (continuous variables) and the two-tailed Fisher’s exact test (categorical variables). Risk factors for seropositivity were analyzed using multivariate logistic regression.

Results: A total of 2;219 workers were included and 847 of them (38.2%) presented IgG antibodies against SARS-CoV-2; being seroprevalence significantly higher for HCW (39.3%) than for nHCW (30.7%; p=0.006). We found no differences regarding positivity rates compared with the first diagnostic approach for symptomatic and asymptomatic workers; or infected workers per professional category. In the multivariate logistic regression analysis; the use of PPE (protective; OR=0.65; 95%CI: 0.48–0.89; p<0.001) and previous contact with COVID-19 patients (risk factor; OR=1.93; 95%CI: 1.37–2.72; p<0.001) were independent factors that were associated with SARS-CoV-2 seropositivity.

Conclusions: More than 38% of our workers presented IgG antibodies against SARS-CoV-2. We found no differences in the positivity rates between diagnostic approaches. The use of PPE (protective) and previous contact with COVID-19 patients (risk factor) were associated with infection.