Background Understanding the drivers of SARS-CoV-2 transmission is crucial for control policies but evidence of transmission rates in different settings remains limited. Methods We conducted a systematic review to estimate secondary attack rates (SAR) and observed reproduction numbers (Robs) in different settings exploring differences by age, symptom status, and duration of exposure. To account for additional study heterogeneity, we employed a Beta-Binomial model to pool SARs across studies and a Negative-binomial model to estimate Robs. Results Households showed the highest transmission rates, with a pooled SAR of 21.1% (95%CI:17.4%-24.8%). SARs were significantly higher where the duration of household exposure exceeded 5 days compared with exposure of ≤5 days. SARs related to contacts at social events with family and friends were higher than those for low-risk casual contacts (5.9% vs. 1.2%). Estimates of SAR and Robs for asymptomatic index cases were approximately a seventh, and for pre-symptomatic two thirds of those for symptomatic index cases. We found some evidence for reduced transmission potential both from and to individuals under 20 years of age in the household context, which is more limited when examining all settings. Conclusions Our results suggest that exposure in settings with familiar contacts increases SARS-CoV-2 transmission potential. Additionally, the differences observed in transmissibility by index case symptom status and duration of exposure have important implications for control strategies such as contact tracing, testing and rapid isolation of cases. There was limited data to explore transmission patterns in workplaces, schools, and care-homes, highlighting the need for further research in such settings.

Background: Long COVID is a syndrome characterized by the persistence of SARS-CoV-2 infection symptoms. Among HCWs, prolonged COVID symptoms could lead to the inability to perform work tasks. The aim of this study is to investigate 35-day long-COVID (35-LC) characteristics and risk factors in a one-year period. Methods: We carried out a retrospective cohort study during the COVID-19 pandemic at University Hospital of Bari. A total of 5750 HCWs were tested for close contact with a confirmed case, in the absence of personal protective equipment, or for symptom development. Results: Each positive HCW was investigated for cardiovascular risk factors or respiratory diseases. An amount of 352 HCWs (6.1%) were infected by SARS-CoV-2, and 168 cases evolved to long COVID. The 35-LC group showed mean BMI values higher than the non-35-LC group (25.9 kg/m2 vs. 24.8 kg/m2, respectively), and this difference was significant (p-value: 0.020). Moreover, HCWs who suffered from pulmonary disease (OR = 3.7, CL 95%: 1.35–10.53; p-value = 0.007) or overweight (OR = 1.6 CL 95%: 1.05–2.56; p-value = 0.029) had an increased risk of developing 35-LC. Conclusions: Long COVID is an emerging problem for hospital managers as it may reduce the number of HCWs deployed in the fight against COVID-19. High BMI and previous pulmonary disease could be risk factors for 35-LC development in exposed HCWs.

In the pre-registration trial, data on the efficacy of the BNT162b2 mRNA vaccine against SARS-CoV-2 infection were not collected. The aim of this study was to evaluate vaccine effectiveness (VE) against documented infection. Bari Policlinico University-Hospital healthcare workers (HCWs) who completed the vaccination schedule were matched with HCWs who had refused vaccination. The VE for documented infection was 61.9% (95%CI=19.2–82.0%) 14–20 days after the first dose, 87.9% (95%CI=51.7–97.0%) 21–27 days after the first dose, and 96.0% (95%CI=82.2–99.1) 7 or more days after the second dose. Unvaccinated HCWs remain a concern even in the context of pandemic emergency.

Highlights This study included 3570 healthcare workers underwent naso and oropharyngeal swabs. The workers were divided into two groups based on COVID-19 patient contact type. SARS-CoV-2 infection prevalence is 0.45% (25 workers of 5750 subjected to protocol). We found 0.52% positive in the low-risk group, 13.16% in the high-risk group. Prevention procedures reduce the risk related to SARS-CoV-2 for healthcare workers.

The presence of products containing nanoparticles or nanofibers is rapidly growing. Nanotechnology involves a wide spectrum of industrial fields. There is a lack of information regarding the toxicity of these nanoparticles in aqueous media. The potential acute toxicity of ZnO NPs using two marine crustacean species: the copepod Tigriopus fulvus and the amphypod Corophium insidiosum was evaluated. Acute tests were conducted on adults of T. Fulvus nauplii and C. insidiosum. Both test species were exposed for 96 h to 5 increasing concentrations of ZnO NPs and ZnSO 4 H 2 O, and the endpoint was mortality. Statistical analysis revealed that the mean LC50 values of both ZnO NPs and ZnSO 4 H 2 O (ZnO NPs: F = 59.42; P < 0.0015; ZnSO 4 H 2 O: F = 25.57; P < 0.0015) were significantly lower for Tigriopus fulvus than for Corophium insidiosum. This result confirms that the toxic effect could be mainly attributed to the Zn ions, confirming that the dissolution processes play a crucial role in the toxicity of the ZnO NPs.