Factors Associated with SARS-CoV-2 Infection before Vaccination among European Health Care Workers.

BACKGROUND: Health care workers (HCWs) were on the frontline of the current pandemic. We aimed at identifying determinants of SARS-CoV-2 infection and the effectiveness of personal protection equipment (PPE) worn by HCWs before vaccination. METHODS: We abstracted data on SARS-CoV-2 infection based on positive PCR results and sociodemographic characteristics of 38,793 HCWs from public hospitals and public health authorities from 10 European centers. We fitted cohort-specific multivariate logistic regression models to identify determinants of infection and combined the results using random-effects meta-analyses. RESULTS: The overall prevalence of infection before vaccination among HCWs was 9.58%. Infection was associated with the presence of selected symptoms; no association was found between sociodemographic factors and increased risk of infection. The use of PPE and particularly FFP2/FFP3 masks had a different protective effect during the first and second waves of the COVID pandemic. CONCLUSIONS: The study provides evidence that mask use was the most effective PPE in preventing SARS-CoV-2 infection among HCWs.

Effectiveness of prevention of SARS-CoV-2 transmission among unvaccinated Italian healthcare workers.

BACKGROUND: We aimed to investigate the association between personal protective equipment (PPE) use and SARS-CoV-2 infection among healthcare workers (HCWs). METHODS: We analyzed occupational surveillance contact forms followed by a PCR test notified between March and September 2020 by Italian HCWs. The odds ratios (ORs) and 95% Confidence Intervals (CIs) for positive PCR based on HCWs and contacts characteristics were calculated through multivariable logistic regression models. When multiple contacts were potentially effective for a PCR test, they were weighted by the inverse of their number. RESULTS: Overall, 4,883 contacts reported by 2,952 HCWs were analyzed, and 224 contacts among 144 HCWs had positive PCR. No difference was found according to sex, age, employment, or job title, except for an OR of 0.30 (95%CI 0.11-0.78) for resident physicians, compared to administrative staff. The ORs for use of surgical mask were 0.59 (95%CI=0.40-0.86) for use only by HCW, 0.49 (95%CI=0.22-1.07) only by the infected person, and 0.40 (95%CI=0.27-0.60) by both, compared to use by neither. Use of other PPEs was not associated with infection, while the OR for hand sanitation was 0.61 (95%CI=0.40-0.93). HCWs reporting fever, cough, and asthenia had a higher risk of infection. CONCLUSIONS: Use of surgical masks was associated with a 40-60% lower risk of infection, especially when both HCWs and infected individuals used them. Our results quantify the role played by mask use and hand sanitation in preventing SARS-CoV-2 transmission in high-risk circumstances.

Vaccination Confidence among Healthcare Workers: Results from Two Anamnestic Questionnaires Adopted in the COVID-19 and Influenza Campaign.

BACKGROUND: Following the announcement of the development of COVID-19 vaccines, hesitancy about the safety of vaccinations and their side effects have spread, despite having the approval of international drug agencies. The aim of this study was to test the hypothesis that concern about side effects may have led people to fill out the COVID-19 anamnestic vaccine questionnaire with greater attention compared to the similar instrument used for the influenza vaccination. METHODS: We analyzed vaccination questionnaires of 218 healthcare workers (HCWs) who underwent both COVID-19 and influenza vaccines in 2020/2021. Outcomes included self-reported allergies, chronic pharmacological treatments, and chronic diseases. We tested the difference in prevalence, analyzed differences using the kappa statistics and concordance correlation, and explored factors associated with differences in reporting. RESULTS: HCWs reported more allergies to substances other than drugs and a higher prevalence of chronic drug intake in the COVID-19 questionnaires than in the influenza ones. Technical staff reported more drug allergies than physicians, and other HCWs reported more outcomes than physicians in the COVID-19 questionnaire. CONCLUSIONS: We found that this population of HCWs reported higher conditions during the 2020 COVID-19 vaccination campaign compared to that of the influenza vaccine. The identification of socio-demographic characteristics of the less vaccine-confident HCWs could help in planning targeted interventions to enhance vaccine adherence.

SARS-CoV-2 Breakthrough Infections: Incidence and Risk Factors in a Large European Multicentric Cohort of Health Workers.

BACKGROUND: The research aimed to investigate the incidence of SARS-CoV-2 breakthrough infections and their determinants in a large European cohort of more than 60,000 health workers. METHODS: A multicentric retrospective cohort study, involving 12 European centers, was carried out within the ORCHESTRA project, collecting data up to 18 November 2021 on fully vaccinated health workers. The cumulative incidence of SARS-CoV-2 breakthrough infections was investigated with its association with occupational and social-demographic characteristics (age, sex, job title, previous SARS-CoV-2 infection, antibody titer levels, and time from the vaccination course completion). RESULTS: Among 64,172 health workers from 12 European health centers, 797 breakthrough infections were observed (cumulative incidence of 1.2%). The primary analysis using individual data on 8 out of 12 centers showed that age and previous infection significantly modified breakthrough infection rates. In the meta-analysis of aggregated data from all centers, previous SARS-CoV-2 infection and the standardized antibody titer were inversely related to the risk of breakthrough infection (p = 0.008 and p = 0.007, respectively). CONCLUSION: The inverse correlation of antibody titer with the risk of breakthrough infection supports the evidence that vaccination plays a primary role in infection prevention, especially in health workers. Cellular immunity, previous clinical conditions, and vaccination timing should be further investigated.

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

We aimed at evaluating quantitative IgG response to BNT162b2 COVID-19 vaccine among health care workers (HCW), and exploring the role of demographic, clinical, and occupational factors as predictors of IgG levels. On May 2021, among 6687 HCW at the largest tertiary care University-Hospital of Northwestern Italy, at a median of 15 weeks (Interquartile range-IQR 13.6-16.0) after second-dose, serological response was present in 99.8%. Seropositivity was >97% in all the subgroups, except those self-reporting immunodeficiency (94.9%). Overall, the median serological IgG value was 990 BAU/mL (IQR 551-1870), with most of subjects with previous SARS-CoV-2 infection or with shorter time lapse (2-8 weeks) between vaccination and serology with values in the highest quintile (>2080). At multivariable analysis, significant predictors of lower values were increasing age, male, current smoking, immunodeficiency, recent occupational contacts, and increasing time lapse from vaccination; conversely, previous infection and recent household contacts were significantly associated with higher IgG levels. Subjects with previous infection kept a very high level (around 2000 BAU/mL) up to 120 days. These results, besides supporting a high serological response up to 4-5 months, suggest predictive factors of faster decay of IgG levels that could be useful in tailoring vaccination strategies.

SARS-CoV-2 infection: use and effectiveness of antigenic swab for the health surveillance of healthcare workers.

BACKGROUND:  The gold standard to identify SARS-CoV-2 infections is the Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) on rhino-pharyngeal swabs, but faster and cheaper methods such as antigenic swabs have been developed. A retrospective observational study on antigenic swabs included in the extraordinary health surveillance protocol of a large Hospital in Turin was aimed to assess their performance validity. Methods: From 30 October 2020 to 4 May 2021, 4000 antigenic swabs were carried out in three groups of healthcare workers (HCWs), respectively (i) asymptomatic, (ii) cohabiting with a positive case, and (iii) not recently exposed to the virus.  Results: Overall sensitivity and specificity associated with a prevalence of 1.30% were 26.9%, 97.2%, respectively, the corresponding positive (PPV) and negative predictive value (NPV) being 11.29% and 99.02% [95% IC (99.00 - 99.04)] respectively; a prevalence of 0.29% was observed in the asymptomatic group, among whom sensitivity and specificity were 25.0% and 98.9%, respectively, the corresponding PPV and NPV being 6.25% and 99.78% [95% IC (99.76 - 99.81)], respectively; the cohabitant group showed a prevalence of 21.11%, sensitivity and specificity were 47.4%, 81.7%, respectively, giving rise to a PPV of 40.91% and NPV of 85.29% [95% IC (85.18 - 85.41)] respectively. The prevalence in the not exposed group was 0.77%, sensitivity and specificity were 29.2%, 97.4%, respectively, and PPV and NPV 8.05% and 99.44% [95% IC (99.42 - 99.46)] respectively. Conclusions: Antigenic swabs reduced costs and provided reliable diagnostic results. In the cohabitant group, the higher-prevalence groups showed poor test performances, likely because of the high prevalence of pre-symptomatic illness in this group. Owing to the relatively low NPV, a negative result would still require confirmation with a molecular test to be acceptable for a surveillance program that effectively reduces the virus's intra-hospital spread.

SARS-CoV-2 infection: efficacy of extensive vaccination of the healthcare workforce in a large Italian hospital.

BACKGROUND: A prospective observational study involved 13,787 Health Care Workers (HCWs) of a large hospital to assess the effectiveness of a SARS-CoV-2 mRNA vaccine. METHODS: The daily incidence of infections was estimated from 1st October 2020 to 30th April 2021 and compared with that of the province of Turin (2.26 million). In the middle of this period, a mass vaccination began among HCW, and its effect was assessed. RESULTS: In the first half-period, 1,163 positive HCWs were observed, the average daily incidence rate per 100,000 being 79.58 (± 15.58; 95% CI) compared to 38.54 (± 5.96; 95% CI) in the general population (p<0.001). The vaccination campaign immunized 9,843 HCWs; among them, the average daily incidence was 14.23 (± 2.73; 95% CI) compared to 34.2 (± 2.95; 95% CI) in the province (p<0.001). Among fully vaccinated HCW, 59 cases were observed, giving rise to an incidence of 6.3 (± 2.66; 95% CI) much lower than in the province (p<0.001). In the second half of the observation period, the RR for HCWs compared to the province dropped from 2.07 (1.96 - 2.18; 95% CI; p<0.001) to 0.5 (0.42 - 0.58; 95% CI; p<0.001) and to 0.17 (0.13 - 0.22; 95% CI; p<0.001) for unvaccinated and vaccinated HCWs, respectively. The RR of vaccinate HCW was 0.43 (0.31 - 0.58; 95% CI; p<0.001) compared to unvaccinated. In the second half of the observation period, unvaccinated HCWs had a RR of 0.21 (0.18 - 0.25; 95% CI; p<0.001) as compared to the first one. A linear regression model (R2 = 0.87) showed that every percent increase in vaccinated HCWs lowered daily incidence by 0.94 (0.86 - 1.02; IC 95%; p<0.001). Vaccinated HCWs had a RR of 0.09 (0.07 - 0.12; 95% CI; p<0.001) compared to unvaccinated HCWs, which led to estimated effectiveness of the two-dose vaccine of 91 % (± 3 %; CI 95%) similar to that reported by the manufacturer.

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.

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).

Determinants of SARS-CoV-2 infection in Italian healthcare workers: a multicenter study.

Healthcare workers (HCWs) are at increased risk of being infected with SARS-CoV-2, yet limited information is available on risk factors of infection. We pooled data on occupational surveillance of 10,654 HCW who were tested for SARS-CoV-2 infection in six Italian centers. Information was available on demographics, job title, department of employment, source of exposure, use of personal protective equipment (PPEs), and COVID-19-related symptoms. We fitted multivariable logistic regression models to calculate odds ratios and 95% confidence intervals of infection. The prevalence of infection ranged from 3.0 to 22.0%, and was correlated with that of the respective areas. Women were at lower risk of infection compared to men. Fever, cough, dyspnea and malaise were the symptoms most strongly associated with infection, together with anosmia and ageusia. No differences in the risk of infection were detected according to job title, or working in a COVID-19 designated department. Reported contact with a patient inside or outside the workplace was a risk factor. Use of a mask was strongly protective against risk of infection as was use of gloves. The use of a mask by the source of exposure (patient or colleague) had an independent effect in reducing infection risk.

Assessment of air and surfaces contamination in a COVID-19 non-Intensive Care Unit.

BACKGROUND: Severe Acute Respiratory Syndrome - Coronavirus - 2 (SARS-CoV-2)  is a virus, primarily transmitted through  droplets, able to persist on different surfaces and in the air for several hours. During the COVID-19 pandemic, Health Care Workers should be considered a high risk profession. Beside social distancing rules and the proper use of Personal Protective Equipment,  sanitization measures and ventilation system disinfection are essential to reduce viral transmission. OBJECTIVES: This is the first Italian study aiming to assess the magnitude of environmental contamination in a COVID-19 non-Intensive Care Unit. METHODS: In addition to ordinary cleaning procedures, surface and air samplings have been performed before and after the application of two different sanitization devices. Samples have been analyzed with Real Time-Polymerase Chain Reaction in order to find viral RNA. RESULTS: All samples obtained from surfaces and air before and after extra-ordinary sanitization procedures turned out negative for viral detection. DISCUSSION: These findings highlight the efficiency of ordinary cleaning procedures in guaranteeing a safer workplace. The adoption of additional sanitization protocols should be considered in order to further reduce environmental viral contamination.

COVID-19 infection and diffusion among the healthcare workforce in a large university-hospital in northwest Italy.

Backgroud: Since the beginning of the coronavirus disease 2019 (COVID-19) outbreak, healthcare workers (HCWs) have been the workers most likely to contract the disease. Intensive focus is therefore needed on hospital strategies that minimize exposure and diffusion, confer protection and facilitate early detection and isolation of infected personnel. METHODS: To evaluate the early impact of a structured risk-management for exposed COVID-19 HCWs and describe how their characteristics contributed to infection and diffusion. Socio-demographic and clinical data, aspects of the event-exposure (date, place, length and distance of exposure, use of PPE) and details of the contact person were collected. RESULTS: The 2411 HCWs reported 2924 COVID-19 contacts. Among 830 HCWs who were at 'high or medium risk', 80 tested positive (9.6%). Physicians (OR=2.03), and non-medical services -resulted in an increased risk (OR=4.23). Patient care did not increase the risk but sharing the work environment did (OR=2.63). There was a significant time reduction between exposure and warning, exposure and test, and warning and test since protocol implementation. HCWs with management postitions were the main source of infection due to the high number of interactions. DISCUSSION: A proactive system that includes prompt detection of contagious staff and identification of sources of exposure helps to lower the intra-hospital spread of infection. A speedier return to work of staff who would otherwise have had to self-isolate as a precautionary measure improves staff morale and patient care by reducing the stress imposed by excessive workloads arising from staff shortages.