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

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.

Prolonged COVID-19 symptom duration in people with systemic autoimmune rheumatic diseases: results from the COVID-19 Global Rheumatology Alliance Vaccine Survey

“…Several reasons for this observation of calendar time with risk of prolonged COVID-19 symptom duration could be considered. First, this period coincided with the wide availability of highly effective vaccines and treatment options (eg, monoclonal antibodies in the outpatient setting), suggesting that vaccination against COVID-19 or outpatient treatment may shorten the duration of viral shedding and reduce the likelihood of developing prolonged symptoms, as reported for the general population 28–32. Second, it is possible that specific circulating variants may impact symptom duration 33.…”

“…First, this period coincided with the wide availability of highly effective vaccines and treatment options (eg, monoclonal antibodies in the outpatient setting), suggesting that vaccination against COVID-19 or outpatient treatment may shorten the duration of viral shedding and reduce the likelihood of developing prolonged symptoms, as reported for the general population. [28][29][30][31][32] Second, it is possible that specific circulating variants may impact symptom duration. 33 Third, differential recall bias, where people with more recent onset of COVID-19 more accurately reported the end of symptoms, may have affected reporting.…”

High Incidence of SARS-CoV-2 Variant of Concern Breakthrough Infections Despite Residual Humoral and Cellular Immunity Induced by BNT162b2 Vaccination in Healthcare Workers: A Long-Term Follow-Up Study in Belgium

“…One might comment that the observed discrepancy in incidence is related to the investigated study population because healthcare workers are more likely to be frequently exposed to infectious doses of viral particles compared to the general population. However, multiple cohorts that monitored BTI incidence in at least 1000 fully vaccinated (i.e., two doses) healthcare workers published incidence rates varying between 0.3 and 1.38% [78][79][80]. On the contrary, one report that compared the influence of a booster vaccine on BTI incidence noted a 21.4% incidence (85/398) within the two-dose regimen control group, which is more similar with the incidence seen in our trial [81].…”

Effectiveness of mRNA and viral‐vector vaccines in epidemic period led by different SARS‐CoV‐2 variants: A systematic review and meta‐analysis

“…Twelve reviews were excluded from the 77 studies, 21 studies lacked sufficient data, two studies were related to inactivated vaccine, 58,59 and two studies were duplicated 24,60 . Finally, 40 studies out of total 1043 abstracts were finally included in our meta‐analysis, 16–54,60 involving 62 954 861 participates and two kinds of COVID‐19 mRNA vaccines, namely BNT162b2 and mRNA‐1273; two kinds of viral vector vaccines, namely ChAdOx1 and Ad26. COV2.S.…”