Prevalence, Persistence, and Factors Associated with SARS-CoV-2 IgG Seropositivity in a Large Cohort of Healthcare Workers in a Tertiary Care University Hospital in Northern Italy

Abstract

This observational study evaluated SARS-CoV-2 IgG seroprevalence and related clinical, demographic, and occupational factors among workers at the largest tertiary care University-Hospital of Northwestern Italy and the University of Turin after the first pandemic wave of March–April 2020. Overall, about 10,000 individuals were tested; seropositive subjects were retested after 5 months to evaluate antibodies waning. Among 8769 hospital workers, seroprevalence was 7.6%, without significant differences related to job profile; among 1185 University workers, 3.3%. Self-reporting of COVID-19 suspected symptoms was significantly associated with positivity (Odds Ratio (OR) 2.07, 95%CI: 1.76–2.44), although 27% of seropositive subjects reported no previous symptom. At multivariable analysis, contacts at work resulted in an increased risk of 69%, or 24% for working in a COVID ward; contacts in the household evidenced the highest risk, up to more than five-fold (OR 5.31, 95%CI: 4.12–6.85). Compared to never smokers, being active smokers was inversely associated with seroprevalence (OR 0.60, 95%CI: 0.48–0.76). After 5 months, 85% of previously positive subjects still tested positive. The frequency of SARS-COV-2 infection among Health Care Workers was comparable with that observed in surveys performed in Northern Italy and Europe after the first pandemic wave. This study confirms that infection frequently occurred as asymptomatic and underlines the importance of household exposure, seroprevalence (OR 0.60, 95%CI: 0.48–0.76).

The Synergistic Effect of Time of Exposure, Distance and No Use of Personal Protective Equipment in the Determination of SARS-CoV-2 Infection: Results of a Contact Tracing Follow-Up Study in Healthcare Workers

“…The incidence of positives among HCWs in our experience is similar to that found by Lahner et al [ 8 ] and much lower if compared to what was found by Scozzari et al and Fong et al [ 9 , 10 ], testifying the effectiveness of the preventive measures. The percentage of positives among supervised operators is double among nurses compared to doctors (respectively, 4.5% vs. 1.9%), a trend also found in a Chinese study concerning the first months of the pandemic [ 11 ].…”

Factors Influencing Level and Persistence of Anti SARS-CoV-2 IgG after BNT162b2 Vaccine: Evidence from a Large Cohort of Healthcare Workers

“…In particular, in Italy, the vaccination campaign started at the end of 2020 with the administration of BNT162b2 vaccine (Pfizer/BioNTech) to healthcare personnel and elderly individuals in nursing homes. In 2020, we conducted an observational study on SARS-CoV-2 IgG seroprevalence in relation to clinical, demographic, and occupational factors among health care, administrative, and service personnel, at a large tertiary care university hospital in Turin [ 1 ]. Currently, the dynamics and magnitude of serological response in vaccinated individuals are being monitored in terms of levels and duration of anti-spike IgG antibodies.…”

Update Alert 10: Epidemiology of and Risk Factors for Coronavirus Infection in Health Care Workers

“…Thirteen new studies reported on the association between exposures and likelihood of infection ( Supplement Table 3 ) ( 6–8 , 11 , 12 , 14 , 16 , 17 , 19 , 20 , 23–25 ). Seven studies ( 7 , 8 , 12 , 19 , 20 , 23 , 24 ) consistently found that exposure to COVID-19 in a household or private setting was associated with increased risk for SARS-CoV-2 infection in HCWs (adjusted odds ratios [ORs] ranged from 2.55 to 8.98) ( Supplement Table 3 ). In most studies, household or private setting exposure was a stronger risk factor than work exposure.…”