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Background: In light of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic, the influence of influenza vaccination on the risk and severity of Coronavirus Disease 19 (COVID-19) has been a subject of debate. This systematic review and meta-analysis of prospective studies aim to assess the association between influenza immunization and the risk of SARS-CoV-2 infection and subsequent COVID-19 disease severity., Methods: A comprehensive search of PubMed and Embase databases was performed to identify prospective studies published before March 2024. We focused on evaluating the effect of influenza vaccination on SARS-CoV-2 infection risk and severe COVID-19 outcomes, such as hospitalization and mortality. The analysis employed a multilevel random effects meta-analysis approach. The risk of bias assessment was conducted using the Newcastle-Ottawa Scale., Results: From an initial pool of 5,863 records, 14 studies were selected for inclusion. The aggregated data yielded a summary relative risk (SRR) that showed no significant protective correlation between influenza vaccination and SARS-CoV-2 infection risk (SRR 0.95, 95% confidence interval [CI] 0.81-1.11), COVID-19-associated hospitalization (SRR 0.90, 95% CI 0.68-1.19), or COVID-19-related mortality (SRR 0.83, 95% CI 0.56-1.23)., Conclusions: This systematic review and meta-analysis, based exclusively on prospective studies, demonstrates the lack of a proven protective effect of influenza vaccination against COVID-19 and related outcomes. Our results do not support a significant protective effect of influenza vaccination against the risk or severe outcomes of COVID-19., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Early after the start of the COVID-19 pandemic, the detection of influenza B/Yamagata cases decreased globally. Given the potential public health implications of this decline, in this Review, we systematically analysed data on influenza B/Yamagata virus circulation (for 2020-23) from multiple complementary sources of information. We identified relevant articles published in PubMed and Embase, and data from the FluNet, Global Initiative on Sharing All Influenza Data, and GenBank databases, webpages of respiratory virus surveillance systems from countries worldwide, and the Global Influenza Hospital Surveillance Network. A progressive decline of influenza B/Yamagata detections was reported across all sources, in absolute terms (total number of cases), as positivity rate, and as a proportion of influenza B detections. Sporadically reported influenza B/Yamagata cases since March, 2020 were mostly vaccine-derived, attributed to data entry errors, or have yet to be definitively confirmed. The likelihood of extinction necessitates a rapid response in terms of reassessing the composition of influenza vaccines, enhanced surveillance for B/Yamagata, and a possible change in the biosafety level when handling B/Yamagata viruses in laboratories., Competing Interests: Declaration of interests MCN received grants from the Foundation for Influenza Epidemiology, Bill & Melinda Gates Foundation, European & Developing Countries Clinical Trials Partnership (EDCTP), Sanofi, AstraZeneca, and Pfizer; received payments or honoraria (for lectures, presentations, speakers bureaus, manuscript writing, or educational events) and support for attending meetings or travel, or both, from Sanofi; and had leadership or fiduciary role from Gavi Board. An unrestricted research grant from NIVEL (the employer) and Sanofi for JP funded the work carried out in this manuscript; JP also received grants or contracts from Sanofi and the Fondation de France; and support for attending meetings or travel, or both, from WHO and Sanofi. The other authors declare no conflicts of interest., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: The COVID-19 pandemic significantly changed respiratory viruses' epidemiology due to non-pharmaceutical interventions and possible viral interactions. This study investigates whether the circulation patterns of respiratory viruses have returned to pre-pandemic norms by comparing their peak timing and duration during the first three SARS-CoV-2 seasons to pre-pandemic times., Methods: Global Influenza Surveillance and Response System data from 194 countries (2014-2023) was analyzed for epidemic peak timing and duration, focusing on pre-pandemic and pandemic periods across both hemispheres and the intertropical belt. The analysis was restricted to countries meeting specific data thresholds to ensure robustness., Results: In 2022/2023, the northern hemisphere experienced earlier influenza and respiratory syncytial virus (RSV) peaks by 1.9 months (P <0.001). The duration of influenza epidemics increased by 2.2 weeks (P <0.001), with RSV showing a similar trend. The southern hemisphere's influenza peak shift was not significant (P = 0.437). Intertropical regions presented no substantial change in peak timing but experienced a significant reduction in the duration for human metapneumovirus and adenovirus (7.2 and 6.5 weeks shorter, respectively, P <0.001)., Conclusions: The pandemic altered the typical patterns of influenza and RSV, with earlier peaks in 2022 in temperate areas. These findings highlight the importance of robust surveillance data to inform public health strategies on evolving viral dynamics in the years to come., Competing Interests: Declaration of Competing Interest MH and ImG are employees of CSL Seqirus and may hold shares. JP declares that Nivel has received research grants which concern the epidemiology of influenza and vaccination against influenza from WHO, Sanofi, and the Foundation for Influenza Epidemiology. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: National Influenza Centers (NICs) have played a crucial role in the surveillance of SARS-CoV-2. The FluCov project, covering 22 countries, was initiated to monitor the impact of the SARS-CoV-2 pandemic on influenza activity., Methods: This project consisted of an epidemiological bulletin and NIC survey. The survey, designed to assess the impact of the pandemic on the influenza surveillance system, was shared with 36 NICs located across 22 countries. NICs were invited to reply between November 2021 and March 2022., Results: We received 18 responses from NICs in 14 countries. Most NICs (76%) indicated that the number of samples tested for influenza decreased. Yet, many NICs (60%) were able to increase their laboratory testing capacity and the "robustness" (e.g., number of sentinel sites) (59%) of their surveillance systems. In addition, sample sources (e.g., hospital or outpatient setting) shifted. All NICs reported a higher burden of work following the onset of the pandemic, with some NICs hiring additional staff or partial outsourcing to other institutes or departments. Many NICs anticipate the future integration of SARS-CoV-2 surveillance into the existing respiratory surveillance system., Discussion: The survey shows the profound impact of SARS-CoV-2 on national influenza surveillance in the first 27 months of the pandemic. Surveillance activities were temporarily disrupted, whilst priority was given to SARS-CoV-2. However, most NICs have shown rapid adaptive capacity underlining the importance of strong national influenza surveillance systems. These developments have the potential to benefit global respiratory surveillance in the years to come; however, questions about sustainability remain., Competing Interests: JP, MDR, SC, and LS declare that Nivel has previously received RSV research grants from Sanofi Pasteur/AstraZeneca, the Foundation for Influenza Epidemiology, and the European Union's Innovative Medicines Initiative. CEG, ED, and MA are Sanofi employees and may hold shares and/or stock options in the company. The other authors have no conflicts of interest to declare., (© 2023 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

We analysed the influenza epidemic that occurred in Australia during the 2022 winter using an age-structured dynamic transmission model, which accounts for past epidemics to estimate the population susceptibility to an influenza infection. We applied the same model to five European countries. Our analysis suggests Europe might experience an early and moderately large influenza epidemic. Also, differences may arise between countries, with Germany and Spain experiencing larger epidemics, than France, Italy and the United Kingdom, especially in children., (© 2022 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

Identifying determinants of COVID-19 vaccine uptake is essential for developing effective strategies for promoting vaccination. This longitudinal study aimed to explore predictors of actual COVID-19 vaccine uptake in workers involved in essential services during the first lockdown period in the Prato Province (Italy). All essential workers were invited and surveyed before COVID-19 vaccine approval (96.5% participation rate). Participants were followed up to evaluate their actual COVID-19 vaccination uptake using the vaccination register. Multinomial models were performed to assess predictors of delayed vaccination or non-vaccination. A total of 691 participants were included, of whom 21.7% had delayed the vaccination and 4.4% were unvaccinated. Participants with a sufficient level of health literacy were 50.2% in the vaccinated-on-time group and 32.3% in the unvaccinated group. The multinomial model predictors of delayed vaccination were work type (OR = 0.51), age between 50 and 59 years (OR = 1.82), and influenza vaccination uptake in the last season (OR = 2.51). Predictors of being unvaccinated were work type (OR = 0.33) and attitudes related to attributing less importance to COVID-19 preventive measures (OR = 0.47). Findings showed distinct predictors for COVID-19 vaccination delay and for being unvaccinated. Being unvaccinated seems to be associated with a general skepticism toward prevention measures.

While two influenza B virus lineages have co-circulated, B/Yamagata-lineage circulation has not been confirmed since March 2020. The WHO FluNet database indicates that B/Yamagata-lineage detections were reported in 2021 and 2022. However, detections can result from use of quadrivalent live-attenuated vaccines. Of the type B viruses detected post-March 2020, all ascribed to a lineage have been B/Victoria-lineage. There is need for a global effort to detect and lineage-ascribe type B influenza viruses, to assess if B/Yamagata-lineage viruses have become extinct.

Annual influenza vaccination is recommended for volunteers involved in primary health and social services. Little is known about the volunteers' adhesion to influenza vaccination recommendations. The aim of this study was to assess influenza vaccination determinants among a group of volunteers who provided essential activities during the first SARS-CoV-2 pandemic wave in the province of Prato, Tuscany (Italy) and to evaluate the role of health literacy in influencing vaccination determinants., Method: In this cross-sectional study, the predictors of influenza vaccination uptake were assessed through the administration of a questionnaire. Variables significantly associated with influenza vaccination uptake were included in five multivariate logistic regression models through a backward stepwise procedure., Results: Among the 502 enrolled volunteers, 24.3% reported being vaccinated in the 2019-2020 season. Vaccination uptake was 48.8% in participants aged 65 years or older and 15.7% in those aged 64 years or younger. Considering the whole sample in the final model of multivariate logistic regression analysis, the predictors of influenza vaccination uptake were age (OR = 1.05; 95% CI = 1.03-1.07), presence of heart diseases (OR = 2.98; 95% CI = 1.24-7.19), pulmonary diseases (OR = 6.18; 95% CI = 2.01-19.04) and having undergone surgery under general anesthesia in the prior year (OR = 3.14; 95% CI = 1.23-8.06). In the multivariate model considering only participants with a sufficient level of health literacy (HL), none of these predictors resulted in significant associations with vaccination uptake, except for age (OR= 1.04; 95% CI = 1.02-1.07)., Conclusions: Our findings revealed a very low influenza vaccination uptake among volunteers, suggesting the need to increase awareness in this at-risk group by means of a better communication approach.

We reviewed the association between seasonal influenza vaccination and the risk of SARS-CoV-2 infection or complicated illness or poor outcome (e.g., severe disease, need for hospitalization or ventilatory support, or death) among COVID-19 patients. None of the studies that were reviewed ( n = 12) found a significant increase in the risk of infection or in the illness severity or lethality, and some reported significantly inverse associations. Our findings support measures aimed at raising influenza vaccination coverage in the coming months.

Introduction : Influenza vaccination is recommended for caregivers of elderly people. In a study aimed at assessing the level of health literacy (HL) in a sample non-familial caregivers in the Florence Health District (Tuscany), data were collected regarding access and adherence to the flu vaccination campaigns. Methods : The sample consists of 47 non-familial paid caregivers. We collected information regarding socio-demographic characteristics, services provided and daily work time, whether or not influenza vaccination was administered for the 2016/2017 season and in the previous three years. The level of HL was assessed through the Newest Vital Sign. Results : 63.8% of non-familial caregivers have not joined the flu campaigns over the last four years, 14.9% have been vaccinated only sometimes (in some epidemic seasons), and 21.3% have received a flu shot in all the seasons investigated. Most of the non-familial caregivers who do not get vaccinated (27.7%) do not perceive that they are in direct contact with a person at-risk; those who get the vaccine regularly (12.8%) reported they want to protect the assisted person as motivation for vaccine uptake. Vaccination was not associated with HL. Conclusion : Adhesion to anti-flu vaccination campaigns for these homecare workers has been resulted rather poor. Coverage does not seem to be related with HL level. It seems appropriate to promote extensively flu vaccination among family carers by actively offering the vaccination in appropriate forms, places and times, to avoid serious consequences on elderly people with higher risk of comorbidity and frailty.