Delay between COVID-19 complete vaccination and SARS-CoV-2 infection among healthcare workers

ObjectivesHealthcare workers (HCWs), at increased risk of coronavirus disease 2019 (COVID-19) were among the primary targets for vaccination, which became mandatory for them on September 15th, 2021 in France. In November they were confronted to the fifth COVID-19 wave despite excellent vaccine coverage. We aimed to estimate the incidence of SARS-CoV-2 infection after complete vaccination among HCWs with different vaccination schemes, and its determinants.MethodsWe enrolled all HCWs in the university hospital of Rennes, France who had received complete vaccination (two doses of COVID-19 vaccine). The delay from last vaccination dose to SARS-CoV-2 infection was computed. Fitted mixed Cox survival model with a random effect applied to exposure risk periods to account for epidemic variation was used to estimate the determinants of SARS-CoV-2 infection after complete vaccination.ResultsOf the 6674 (82%) HCWs who received complete vaccination (36% BNT162b2, 29% mRNA-1273, and 34% mixed with ChAdOx1 nCoV-19) and were prospectively followed-up for a median of 7.0 [6.3–8.0] months, 160 (2.4%) tested positive for SARS-CoV-2 by RT-PCR. Incidence density of SARS-CoV-2 infection after complete vaccination was 3.39 [2.89–3.96] infections per 1000 person-month. Median time from vaccine completion to SARS-CoV-2 infection was 5.5 [3.2–6.6] months. Using fitted mixed Cox regression with the delay as a time-dependent variable and random effect applied to exposure risk periods, age (P < 0.001) was independently associated with the incidence of SARS-CoV-2 infection. Vaccine schemes were not associated with SARS-CoV-2 infection (P = 0.068). A period effect was significantly associated with the incidence of SARS-CoV-2 infection (P < 0.001).ConclusionsIn this real-world study, incidence of SARS-CoV-2 infection increases with time in fully vaccinated HCWs with no differences according to the vaccination scheme. The short delay between complete vaccination and incident SARS-CoV-2 infection highlights the need for sustained barrier measures even in fully vaccinated HCWs.     

The effect of immunization with inactivated SARS-CoV-2 vaccine (CoronaVac) and/or SARS-CoV-2 infection on antibody levels,plasmablasts, long-lived-plasma-cells,and IFN-γ release by natural killer cells

ObjectivesWe evaluated the antibody response, natural killer cell response and B cell phenotypes in healthcare workers (HCW) who are vaccinated with two doses of CoronaVac with or without documented SARS-CoV-2 infection and unvaccinated HCWs with SARS-CoV-2 infection.MethodsHCWs were divided into four groups: vaccine only (VO), vaccine after SARS-CoV-2 infection (VAI), SARS-CoV-2 infection only (IO), and SARS-CoV-2 infection after vaccine (IAV). Anti-SARS-CoV-2 spike protein (Anti-S) antibodies were measured by Elecsys Anti–SARS–CoV–2 S ELISA kit. Memory B cells (CD19⁺CD27⁺), plasmablast B cells (CD19⁺CD138⁺) and long-lived plasma cells (LLPC; CD138⁺CD19^-) were measured by flow cytometry in 74 patients. Interferon gamma (IFN-γ) release by natural killer (NK) cells were measured by NKVue Test (NKMAX, Republic of Korea) in 76 patients. RT-PCR was performed with Bio-speedy® COVID-19 qPCR detection kit, Version 2 (Bioexen LTD, Istanbul, Turkey).ResultsThe Anti-S antibodies were detectable in all HCWs (n: 224). The median Anti-S titers (BAU/mL) was significantly higher in VAI (620 25–75% 373–1341) compared to VO (136, 25–75% 85–283) and IO (111, 25–75% 54–413, p < 0.01). VAI group had significantly lower percentage of plasmablasts (2.9; 0–8.7) compared to VO (6.8; 3.5–12.0) and IO (9.9; 4.7–47.5, p < 0.01) (n:74). Percentage of LLPCs in groups VO, VAI and IO was similar. There was no difference of IFN-γ levels between the study groups (n: 76).ConclusionThe antibody response was similar between uninfected vaccinated HCWs and unvaccinated HCWs who had natural infection. HCWs who had two doses of CoronaVac either before or after the natural SARS-CoV-2 infection elicited significantly higher antibody responses compared to uninfected vaccinated HCWs. The lower percentages of plasmablasts in the VAI group may indicate their migration to lymph nodes and initiation of the germinal center reaction phase. IFN-γ response did not differ among the groups.     

Effect of the 2020/21 season influenza vaccine on SARS-CoV-2 infection in a cohort of Italian healthcare workers

ObjectivesHealthcare workers (HCWs) are a priority group for seasonal influenza vaccination (SIV). The 2020/21 SIV campaign was conducted during the second wave of the COVID-19 pandemic. Vaccines, including SIV, may exert non-specific protective effects on other infectious diseases which may be ascribable to the concept of trained immunity. The aim of this study was to explore the association between 2020/21 SIV and SARS-CoV-2 positivity in a cohort of Italian HCWs.MethodsIn this observational study, a cohort of HCWs employed by a large (ca 5000 employees) referral tertiary acute-care university hospital was followed up retrospectively until the start of the COVID-19 vaccination campaign. The independent variable of interest was the 2020/21 SIV uptake. Both egg-based and cell culture-derived quadrivalent SIVs were available. The study outcome was the incidence of new SARS-CoV-2 infections, as determined by RT-PCR. Multivariable Cox regression was applied in order to discern the association of interest.ResultsThe final cohort consisted of 2561 HCWs who underwent ≥1 RT-PCR test and accounted for a total of 94,445 person-days of observation. SIV uptake was 35.6%. During the study period, a total of 290 new SARS-CoV-2 infections occurred. The incidence of new SARS-CoV-2 was 1.62 (95% CI: 1.22–2.10) and 3.91 (95% CI: 3.43–4.45) per 1000 person-days in vaccinated and non-vaccinated HCWs, respectively, with an adjusted non-proportional hazard ratio of 0.37 (95% CI: 0.22–0.62). E-values suggested that unmeasured confounding was unlikely to explain the association.ConclusionsA lower risk of SARS-CoV-2 infection was observed among SIV recipients.     

COVID-19 vaccine confidence and reasons for vaccination among health care workers and household members

BackgroundThe majority of healthcare workers (HCW) in the US report being fully vaccinated against COVID-19, yet little is known about vaccine decision-making for their household members, including children.MethodsCross-sectional survey July–August 2021 of HCW and their household members in Minnesota.Results94 % of eligible participants were vaccinated with the most common reasons being wanting to protect oneself, family and loved ones. Safety concerns were the most commonly reported reasons for not being vaccinated; a significantly higher proportion of unvaccinated compared to vaccinated HCW (58 % vs 12 %, p = 0.0035) and household adults (25 % vs 5 %, p = 0.03) reported prior SARS-CoV-2 infection. Nearly half of unvaccinated adults and two-thirds of unvaccinated children would be vaccinated if a vaccine mandate were in place.ConclusionsDespite high COVID-19 vaccine acceptance among HCWs, more research is required to identify and address the needs and concerns of healthcare workers who decline COVID-19 vaccination despite availability.     

Epidemiology of SARS-CoV-2 among healthcare workers in North-Eastern Italy from March 1, 2020 to May 10, 2020

Background:During major epidemic outbreaks, the preparedness of public health systems is challenged and healthcare workers (HCWs) are at the frontline. Italy was among the first- and worst-hit countries by COVID-19.Aim:To analyze the prevalence and incidence of infection among HCWs in Friuli Venezia Giulia region (north-eastern Italy) from March 1 to the end of the Italian lock-down, May 10, 2020. Methods. HCWs exposed to COVID-19 patients were actively surveyed and all HCWs were routinely tested with nasopharyngeal and oropharyngeal swab for RNA virus detection (n. 54,670).Results:Infected HCWs (n. 595) represented the 32.3% of all COVID-19 cases in the region under 65 years of age, and incidence of infection was 11.4 cases/1000 workers. HCWs accounted for a significant proportion of coronavirus infection and experienced high infection incidence after unprotected contact. Conclusions. HCWs’ knowledge of SARS-CoV-2 epidemiology and proper infection control practices are critical to the control of the disease.     

Side effects among healthcare workers from a large Milan university hospital after second dose of BNT162b2 mRNA COVID-19 vaccine

Background:In Italy, healthcare workers (HCWs) were among the first to receive COVID-19 vaccination. Aim of the present study is to evaluate frequency and severity of adverse events (AEs) following the second dose of BNT162b2 vaccine among HCWs of a large university hospital in Milan, Italy.Methods:One month after having received the second dose of vaccine, HCWs filled-in a form about type, severity, and duration of post-vaccination local and systemic symptoms. We calculated the overall frequency of AEs and used multivariable Poisson regression models (adjusted for sex, age, BMI, smoking, allergy history, previous SARS-CoV-2 infection, anti-hypertensive therapy, and occupation) to calculate risk ratios (RR) and 95% confidence intervals (CI) of AEs according to selected variables.Results:We included 3659 HCWs. Overall, 2801 (76.6%) experienced at least one local event, with pain at injection site being the most frequent (2788, 76.2%). Systemic events were reported by 2080 (56.8%) HCWs, with fatigue (52.3%), muscle pain (42.2%), headache (37.7%), joint pain (31.9%), and fever (26.2%) being the most frequent. Risks of systemic events were associated with female gender (RR=1.14, CI: 1.06-1.24), age (strong decrease with increasing age, p-trend<0.001), allergy history (RR=1.13, CI: 1.05-1.20), SARS-CoV-2 infection more than 180 days before second dose (RR=1.16, CI:1.01-1.32), and current smoking (RR=0.90, CI: 0.84-0.97).Conclusions:Both local and systemic acute effects after second dose of BNT162b2 vaccine were frequently reported. However, symptoms were mostly light/mild and of short duration. Thus, our findings support the safety of COVID-19 vaccination in adults in relatively good health.     

Waning effectiveness of CoronaVac in real life: A retrospective cohort study in health care workers

BackgroundReal-world studies showed varying levels of effectiveness of CoronaVac vaccine against COVID-19 disease. This study aimed to assess the association between the vaccination with CoronaVac and the COVID-19 infections among the health care workers in a university hospital and to determine the vaccine effectiveness against COVID-19 in a period when alpha variant was dominant.MethodsThis retrospective cohort study was conducted in a university hospital in Istanbul, Turkey employs 4067 health care workers. The follow-up period was defined as starting 14 days after receiving the second dose for fully vaccinated group. Health care workers were censored when have a positive PCR test result or at the end of the study. Unvaccinated health care workers were censored if they receive any COVID-19 vaccine doses. The incidence rate ratio and Cox regression were used to estimate the unadjusted and adjusted effectiveness of the vaccine.Findings: Seventy-one percent of the health care workers were fully vaccinated whereas 29% percent did not receive any doses. The incidence rate of SARS-CoV-2 infection was 133.7 vs 70.7 per 100.000 person-days in the unvaccinated and fully vaccinated groups, respectively. The unadjusted effectiveness against COVID-19 infection was 47% (95% CI 31–59%) whereas adjusted effectiveness was 39% (95% CI 20–64%).Interpretation: This real life study conducted in health care workers demonstrated that the effectiveness of two doses of the CoronaVac vaccine (39%) was lower than that determined in clinical trials. Due to reduce in protection over time or against variants, booster doses may be needed.     

Change in COVID19 outbreak pattern following vaccination in long-term care facilities in Flanders,Belgium

IntroductionLong term care facilities for elderly (LTCFs) in Europe encountered a high disease burden at the start of the COVID-19 pandemic. Therefore, these facilities were the first to receive COVID-19 vaccines in many European countries. A limited COVID-19 vaccine supply early 2021 resulted in a majority of residents and healthcare workers (HCWs) in LTCFs being vaccinated compared to a minority in the general population. This study exploits this imbalance to assess the efficiency of COVID-19 vaccination in containing outbreaks in LTCFs.MethodsExploratory statistics were performed using data from a COVID-19 surveillance system covering all 842 LTCFs in Flanders (the northern region of Belgium). The number and size of COVID-19 outbreaks in LTCFs were compared (1) before and after introducing vaccines and (2) with the status of the pandemic in the general population. Based on individual data from 15 LTCFs, the infection rate and symptoms of vaccinated and unvaccinated residents and HCWs were compared during a COVID-19 outbreak.Results95.8% of the residents and 90.9% of the HCWs in Flemish LTCFs were vaccinated before May 30, 2021. Before vaccine introduction, residents in LTCFs were 10 times more likely to test positive for COVID-19 than the general population of Flanders. This ratio reversed after vaccination. Furthermore, after vaccination fewer and shorter outbreaks were observed involving fewer residents. During these outbreaks, vaccinated and unvaccinated residents were equally likely to test positive, but positive vaccinated residents were less likely to develop severe symptoms. In contrast, unvaccinated HCWs were more likely to test positive.ConclusionIn the first half of 2021, two-dose vaccination was highly efficient in preventing and containing outbreaks in LTCFs, reducing COVID-19 hospitalizations and deaths. The high likelihood of unvaccinated HCWs to be involved in COVID-19 outbreaks in vaccinated LTCFs emphasizes the importance of vaccinating HCWs.     

BNT162b2 mRNA COVID-19 vaccine Reactogenicity: The key role of immunity

We examined the impact of pre-existing SARS-CoV-2-specific cellular immunity on BNT162b2 mRNA COVID-19 vaccine reactogenicity. Of 96 healthcare workers (HCWs), 76% reported any vaccine reaction (first dose: 70%, second dose: 67%), none of which was severe. Following first dose, systemic reactions were significantly more frequent among HCWs with past infection than in infection-naïve individuals, and among HCWs with pre-existing cellular immunity than in those without it. The rate of systemic reactions after second dose was 1.7 and 2.0-times higher than after first dose among infection-naïve HCWs and those without pre-existing cellular immunity, respectively. Levels of SARS-CoV-2-specific T-cells before vaccination were higher in HCWs with systemic reactions after the first dose than in those without them. BNT162b2 vaccine reactogenicity after first dose is attributable to pre-existing cellular immunity elicited by prior COVID-19 or cross-reactivity. Reactogenicity following second dose suggests an immunity-boosting effect. Overall, these data may reduce negative attitudes towards COVID-19 vaccines.Study Registration.The study was registered on clinicaltrials.gov, NCT04402827.     

Knowledge,attitudes, and practices regarding hepatitis B vaccination among hospital-based doctors and nurses in China: Results of a multi-site survey

BackgroundHepatitis B virus (HBV) can cause chronic HBV infection, which may lead to advanced cirrhosis and liver cancer. Healthcare workers (HCWs) are at risk HBV infection as an occupational hazard. Hepatitis B vaccination of HCWs is recommended by WHO, but the status of hepatitis B vaccination among HCWs in China is seldom reported.MethodologyWe conducted a cross-sectional study in 22 hospitals of 3 developed cities in China. We interviewed managers in infectious diseases and occupational health departments, and at least 40 HCWs per hospital.ResultsWe interviewed 929 HCWs; 80.8% were vaccinated against hepatitis B and 96.7% were willing to be vaccinated; 38.2% of HCWs reported having at least one needle stick or sharps injury. Three hospitals provide free hepatitis B vaccination for HCWs; hospitals with a hepatitis B vaccination policy, more HCWs reported being vaccinated (91.7% vs 79.0%, P < 0.001). HCWs in high risk departments (P = 0.011), with more knowledge of hepatitis B vaccine (P < 0.001), and with fewer working years (P = 0.002) were more likely to be vaccinated against HBV. Infectious diseases and occupational health managers had positive attitudes towards hepatitis B vaccination.ConclusionsHepatitis B vaccination was well accepted among HCWs. Hospital provision of free vaccine, greater HCW knowledge of HBV, and working in higher-risk settings were associated with being vaccinated. A national policy of offering hepatitis B vaccine to HCWs should be considered in China. Provision of free hepatitis B vaccine for HBsAb negative HCWs may be acceptable. Education about HBV and hepatitis B vaccine may help promote policy implementation.     

Safety profile and SARS-CoV-2 breakthrough infections among HCWs receiving anti-SARS-CoV-2 and influenza vaccines simultaneously: an Italian observational study

In October/December 2021, World Health Organization and other international agencies recommended the offer of the third dose of anti-SARS-CoV-2 vaccine. In this period, the routine offer of seasonal influenza vaccination was also guaranteed and simultaneous administration of the two vaccines was encouraged.This study aims to evaluate the safety profile and to estimate the incidence of SARS-CoV-2 breakthrough infections in subjects receiving the anti-SARS-CoV-2 and influenza vaccines simultaneously.The study population was represented by healthcare workers (HCWs) of Bari Policlinico General Hospital who received the influenza (Flucelvax Tetra®) and/or anti-SARS-CoV-2 vaccination (BNT162b2 mRNA COVID-19 vaccine, Comirnaty®) either in coadministration or separately in October 2021. Reports of adverse events following immunization (AEFIs) were investigated to study the safety of both vaccines in coadministration and in separate-instance administration. Post-vaccination SARS-CoV-2 breakthrough infection was also studied.942 HCWs accepted to join our study. 610/942 received both vaccines simultaneously. 25.26 % subjects (238/942) were only vaccinated against SARS-CoV-2, while the remaining 94 HCWs received the influenza vaccination first and subsequently received the anti-SARS-CoV2 booster dose.717 HCWs reported AEFIs (Reporting Rate 76.1 per 100 subjects). Simultaneous administration of the two vaccines was not related with an increase of the rate of AEFIs compared to the single administration of SARS-CoV-2 vaccine, but the AEFIs’ rate was lower among subjects who received only influenza vaccine.Post-vaccination SARS-CoV-2 infections were notified for 41.5 % of enrolled subjects (391/942). Incidence of breakthrough infection and symptomatic disease was not significantly different between the simultaneous administration group and other subjects.Our data suggests that simultaneous administration of a quadrivalent influenza vaccine and an mRNA anti-SARS-CoV-2 vaccine neither affected the safety of said products nor was associated with a higher risk of SARS-CoV-2 breakthrough infection.     

新型冠状病毒疫苗接种对成都市境外输入病例流行病学及临床特征的影响分析

目的 分析新型冠状病毒（新冠病毒）疫苗接种对成都市境外输入病例流行病学及临床特征的影响,为新型冠状病毒肺炎疫情防控提供参考依据。方法 截至2021年4月15日,经成都市入境的新冠病毒感染病例,根据新冠病毒疫苗接种史被分为疫苗接种组和疫苗未接种组。回顾性收集和分析病例的流行病学及临床特征资料。实验室检测项目包括新冠病毒核酸检测、临床指标、血清抗体和淋巴细胞检测。采用WPS 2019软件整理数据,采用R 4.0.3软件进行统计学分析。结果 75例新冠病毒感染病例包括疫苗接种组20例（出现临床症状4例）和疫苗未接种组55例（出现临床症状16例）。疫苗接种组的首针接种时间分布为2020年7-11月,其中接种2剂次疫苗采用一次性接种方式有10例,采取2次间隔接种方式有10例,2次接种间隔14~57 d,完成疫苗接种与发病时间间隔87~224 d。两组病例的分类和临床分型的差异有统计学意义（P<0.05）,其中,疫苗接种组病例分类为无症状感染者的比例较高（40.00%,8/20）,而疫苗未接种组的临床分型以普通型的比例较高（76.36%,42/55）。两组病例的新冠病毒核酸检测2个靶标（ORF1ab和N基因）Ct值、淋巴细胞亚型、降钙素原及C反应蛋白的差异无统计学意义（P>0.05）,疫苗接种组的血清淀粉样蛋白A水平低于疫苗未接种组（P<0.05）,但新冠病毒血清抗体IgM、IgG及总抗体水平均明显高于疫苗未接种组（P<0.05）。结论 新冠病毒疫苗接种后,仍存在感染的风险,但新冠病毒侵入人体后,体内可迅速产生特异性IgM和IgG抗体,对感染者产生一定保护作用,已接种新冠病毒疫苗的病例分类以无症状感染者为主。     

Increased delta variant SARS-CoV-2 infections in a highly vaccinated medical center in Japan

The Delta variant has dominated SARS-CoV-2 infections in Tokyo, Japan from June 2021 to date. We conducted a retrospective cohort study to assess BNT162b2 vaccine effectiveness during the surge in Delta among 3,911 healthcare workers (HCWs) at a medical center of Tokyo with a high vaccination rate of 84.1%. With strict infection control protocols including universal masking, only a small number of cases among vaccinated and unvaccinated HCWs were identified before June. As Delta spread in Tokyo, 16 cases among 3,289 fully vaccinated HCWs and 11 cases among 574 unvaccinated HCWs were reported in July and August (case rate in August: 4.0 vs. 19.2 per 1,000). All breakthrough cases were confirmed as Delta. While our study confirms a robust vaccine effectiveness of BNT162b2 vaccine against Delta, rising breakthrough cases suggest that continued infection control measures are warranted in higher risk environments, even when high rates of vaccination coverage are achieved.     

Disparities in COVID-19 vaccine uptake among health care workers

BackgroundCOVID-19 vaccine uptake by healthcare workers (HCWs) is critical to protect HCWs, the patients they care for, and the healthcare infrastructure. Our study aims to examine the actual COVID-19 vaccination rate among HCWs and identify risk factors associated with vaccine nonacceptance.Study Design and MethodsA retrospective analysis of COVID-19 vaccinations for HCWs at a large multi-site US academic medical center from 12/18/2020 through 05/04/2021. Comparisons between groups were performed using unpaired student t-test for continuous variables and the chi-square test for categorical variables. A logistic regression analysis was used to assess the associations between vaccine uptake and risk factor(s).ResultsOf the 65,270 HCWs included in our analysis, the overall vaccination rate was 78.6%. Male gender, older age, White and Asian race, and direct patient care were associated with higher vaccination rates (P <.0001). Significant differences were observed between different job categories. Physicians and advanced practice staff, and healthcare professionals were more likely to be vaccinated than nurses and support staff.ConclusionsOur data demonstrated higher initial vaccination rates among HCWs than the general population national average during the study period. We observed significant disparities among different high-risk HCWs groups, especially among different job categories, black HCWs and younger HCWs despite their high risk of contracting the infection. Interventions to address lower vaccination rate and vaccine hesitancy should be built with these disparities and differences in mind to create more targeted interventions.     

SARS-CoV-2 infection risk among vaccinated and unvaccinated household members during the Alpha variant surge – Denver,Colorado, and San Diego,California, January–April 2021

BackgroundCOVID-19 vaccination reduces SARS-CoV-2 infection and transmission. However, evidence is emerging on the degree of protection across variants and in high-transmission settings. To better understand the protection afforded by vaccination specifically in a high-transmission setting, we examined household transmission of SARS-CoV-2 during a period of high community incidence with predominant SARS-CoV-2 B.1.1.7 (Alpha) variant, among vaccinated and unvaccinated contacts.MethodsWe conducted a household transmission investigation in San Diego County, California, and Denver, Colorado, during January-April 2021. Households were enrolled if they had at least one person with documented SARS-CoV-2 infection. We collected nasopharyngeal swabs, blood, demographic information, and vaccination history from all consenting household members. We compared infection risks (IRs), RT-PCR cycle threshold values, SARS-CoV-2 culture results, and antibody statuses among vaccinated and unvaccinated household contacts.ResultsWe enrolled 493 individuals from 138 households. The SARS-CoV-2 variant was identified from 121/138 households (88%). The most common variants were Alpha (75/121, 62%) and Epsilon (19/121, 16%). There were no households with discordant lineages among household members. One fully vaccinated secondary case was symptomatic (13%); the other 5 were asymptomatic (87%). Among unvaccinated secondary cases, 105/108 (97%) were symptomatic. Among 127 households with a single primary case, the IR for household contacts was 45% (146/322; 95% Confidence Interval [CI] 40–51%). The observed IR was higher in unvaccinated (130/257, 49%, 95% CI 45–57%) than fully vaccinated contacts (6/26, 23%, 95% CI 11–42%). A lower proportion of households with a fully vaccinated primary case had secondary cases (1/5, 20%) than households with an unvaccinated primary case (66/108, 62%).ConclusionsAlthough SARS-CoV-2 infections in vaccinated household contacts were reported in this high transmission setting, full vaccination protected against SARS-CoV-2 infection. These findings further support the protective effect of COVID-19 vaccination and highlight the need for ongoing vaccination among eligible persons.     

Uptake of COVID-19 vaccines among healthcare workers and the effect of nudging interventions: A mixed methods study

BackgroundDuring the coronavirus disease (COVID-19) pandemic, vaccination of healthcare workers (HCWs) has a critical role because of their high-risk exposure and being a role model. Therefore, we aimed to investigate vaccine hesitancy and the role of mandatory polymerase chain reaction (PCR) testing and education for vaccine uptake.MethodsWe conducted an explanatory sequential designed observational mixed-methods study, including quantitative and qualitative sections consecutively in two different pandemic hospitals between 15 September 2021 and 1 April 2022. The characteristics of vaccinated and unvaccinated HCWs were compared. The vaccine hesitancy scales were applied, and the effect of nudging, such as mandatory PCR and education, were evaluated. In-depth interviews were performed to investigate the COVID-19 vaccine hesitancy among HCWs according to Health Belief Model.ResultsIn total, 3940 HCWs were included. Vaccine hesitancy was more common among males than females, the ancillary workers than other health professions, and nonmedical departments than other departments. After the mandatory weekly PCR request nudge, 83.33 % (130/156) vaccine-hesitant HCWs were vaccinated, and 8.3 % (13/156) after the small group seminars and mandatory PCR every two days. The rate of COVID-19 vaccination was raised from 95.5 % to 99.67 % (3927/3940). At the end of in-depth interviews (n = 13), the vaccine hesitancy determinants were distrust, fear of uncertainty, immune confidence and spirituality, the media effect, social pressure, and obstinacy.ConclusionsThe nudging interventions such as mandatory PCR testing and small group seminars helped raise the rate of COVID-19 vaccination; the most effective one is mandatory PCR.     

COVID-19 impact and vaccine effectiveness among healthcare workers of a large University Hospital in Lombardy,Italy

Background:Healthcare Workers (HCWs) are a key element in managing the COVID-19 pandemic, but they are also at high risk of infection.Objective:The aim of this study was to describe, in a large university hospital which provided healthcare services to patients with SARS-CoV-2 infection, the course of the epidemic among HCWs and effectiveness of COVID-19 vaccination in reducing SARS-CoV-2 infection and disease.Methods:Our case series included all “Fatebenefratelli Sacco” University Hospital workers. Data were collected until the 15th of May 2021 and analysed as part of the health surveillance program carried out by the Occupational Health Unit.Results:From March 2020 until May 2021, 14.4% of workers contracted COVID-19, with the highest incidence peak recorded during the second wave of the pandemic. The prevalence of infection was slightly higher in males than in females, and a greater number of cases was found in job categories characterized by direct patient care activities. We reported a higher prevalence of “serious/critical illness” in elder workers. A clear reduction of COVID-19 incidence was found in our population during the third pandemic wave, that coincided with the start of vaccination campaign.Discussion:HCWs have been at high risk of COVID-19 infection. Male sex and advanced age appear to be predisposing factor and negative prognostic factor respectively. An out-of-hospital setting appears to be the main source of COVID-19 confirming that the correct use of protective devices during work counters the risk of infection. Vaccination seems to reduce both documented cases of infection and severe illness.     

Protection of vaccination versus hybrid immunity against infection with COVID-19 Omicron variants among Health-Care Workers

Background aimThe Omicron COVID-19 variants BA.1* and BA.2* evade immune system leading to increased transmissibility and breakthrough infections. We aim to test the hypothesis that immunity achieved post COVID-19 infection combined with vaccination (hybrid immunity), is more effective against Omicron infection than vaccination alone in a health-care setting.MethodsData on regular pre-emptive PCR testing from all Health-Care Workers (HCWs) at Laiko University Hospital from 29th December 2020, date on which the national COVID-19 immunization program began in Greece, until 24th May 2022, were retrospectively collected and recorded. The infection rate was calculated after December 21st, 2021, when Omicron was the predominant circulating variant in Greece, as the total number of infections (positive PCR COVID-19 test regardless of symptoms) divided by the total person-months at risk.ResultsOf 1,305 vaccinated HCWs who were included in the analysis [median age of 47 (IQR: 36, 56) years, 66.7 % women], 13 % and 87 % had received 2 or 3 vaccine doses (full and booster vaccination), respectively. A COVID-19 infection had occurred in 135 of 1,305 of participants prior to Omicron predominance. Of those 135 HCWs with hybrid immunity only 13 (9.6 %) were re-infected. Of the 154 and 1,016 HCWs with full and booster vaccination-induced immunity, respectively, 71 (46.1 %, infection rate 13.4/100 person-months) and 448 (44.1 %, infection rate 12.2/100 person-months) were infected during the follow up period. No association between gender or age and COVID-19 infection was found and none of the participants had a severe infection or died.ConclusionsHybrid immunity confers higher protection by almost 5-fold compared to full or booster vaccination for COVID-19 infection with the Omicron variant among HCWs who are at high risk of exposure. This may inform public health policies on how to achieve optimal immunity in terms of the timing and mode of vaccination.