SARS-CoV-2 Antibody Prevalence in Health Care Workers of Lodi Hospital, the COVID-19 Italian Epicentre

Background: The prevalence of specific antibodies against SARS-CoV-2 could be regarded as a surrogate measure of effectiveness of infection prevention and control strategies (IPC) for healthcare workers during Italian pandemic outbreak. This paper reports on a survey carried out in April 2020, to assess the prevalence of Sars-Cov-2 IgG-specific in Health Care Workers (HCWs) at Lodi Hospital, a public healthcare centre located in the area of the first epicentre of Italian Covid-19 outbreak, as compared to a sample from the general population from the same area. Method: The IgG title has been determined by the Liaison® DiaSorin® SARS-CoV-2 S1/S2 IgG test in peripheral blood samples of 2415 HCWs and in 1792 people resident in the same area. Socio-demographic variables and job tasks related to the exposure determinants have been considered. Results: The prevalence of HCWs with IgG-specific antibodies was 16.8%. IgG positivity showed correlation with age, job title (healthcare assistant and medical technician), occupational risk exposure (high vs low risk). IgG prevalence among HCWs was significantly lower than in the sample of the Lodi general population (29.8%) (OR= 0.469; 95% CI: 0.405-0.544), p<0.001. Conclusion: In spite of the potentially higher risk of contacts with the SARS­CoV­2 virus in healthcare setting, the HCW population showed a lower prevalence of IgG-specific antibodies as compared to a representative sample of people living in the same area. A possible explanation of such unexpected finding is that the likelihood of intense, continuous and effective contacts is higher in the general population than in trained and protected people. This highlights the need, at the onset of epidemics, to implement an early and multidimensional system of protection of the working population, pointing out to an increasing awareness of healthcare workers towards the SARS-COV-2 transmission pathways.