Post-Vaccination SARS-CoV-2 Infections among Health Workers at the University Hospital of Verona, Italy: A Retrospective Cohort Survey.

Stefano Porru,Virginia Lotti,Giuseppe Verlato,Maria Grazia Lourdes Monaco,Giuseppe Lippi,Alessandro Valotti,Gianluca Spiteri,Angela Carta,Erica Diani,Davide Gibellini

doi:10.3390/vaccines10020272

Abstract

Background: The SARS-CoV-2 vaccination campaign began on 27 December 2020 in Europe, primarily involving health workers. This study aimed to assess the SARS-CoV-2 vaccination effectiveness, as assessed by reductions in incidence, symptom severity, and further infection spreading. Methods: A retrospective cohort study was conducted on 9811 health workers operating at the Verona University Hospital, Italy, from 27 December 2020 to 3 May 2021. All health workers were offered vaccination with Comirnaty (BNT162b2, BioNTech/Pfizer, Mainz, Germany/New York, United States), and a health surveillance program was implemented with periodical swab testing. Vaccination status and clinical data were collected using an ad hoc semi-structured questionnaire and health surveillance charts. Results: As of 3rd of May, 82.5% of health workers had been vaccinated against SAR-CoV-2, and 177 (1.8%) had tested positive for SARS-CoV-2. Vaccination more than halved the cumulative incidence of SARS-CoV-2 infection and reduced by two-thirds the cumulative incidence of symptomatic subjects. In detail, most unvaccinated HWs were symptomatic; 50% reported fever, 45% reported ageusia/anosmia, and nearly 20% reported dyspnea. These percentages were much lower in HWs who had been vaccinated for at least 14 days (18% for fever and anosmia, 6% for dyspnea and ageusia). Moreover, cases of vaccine breakthrough were sixfold less likely to further spread the infection than unvaccinated HWs. Conclusions: SARS-CoV-2 vaccination reduced the infection frequency among HWs, further spreading of the infection, and the presence, severity, and duration of COVID-19-related symptoms.

Highlights

Since the onset of SARS-CoV-2 in December 2019 in Wuhan (China), many countries have experienced multiple waves of outbreaks of this virus
A retrospective cohort study was conducted within an Health workers (HWs) surveillance project framework to assess SARS-CoV-2 vaccination effectiveness among 9811 HWs operating at the University Hospital of Verona, Italy [30,31], one of Italy’s largest hospitals in terms of bed number
The incidence of SARS-CoV-2 infection among HWs of the University Hospital of Verona was 101.4 per 100,000 per week during the observation period

Summary

Introduction

Since the onset of SARS-CoV-2 in December 2019 in Wuhan (China), many countries have experienced multiple waves of outbreaks of this virus. 319 million cases have been diagnosed worldwide; over 5,500,000 were fatal [1,2]. Was one of the first affected countries, with more than 5 million confirmed cases and about. 138,000 deaths caused by the infection [3,4]. Health workers (HWs) are the category most exposed to infection; since February 2020, about 150,000 cases have been diagnosed among. With over 9000 hospital admissions [4]. Since the pandemic’s beginning, an enormous effort to reduce the pandemic’s impact has involved the entire scientific community.

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