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Background: This study aimed to establish a Severity Scale for influenza and other acute respiratory infections (ARI), requiring hospitalization, for surveillance and research purposes (the SevScale). Such a scale could aid the interpretation of data gathered from disparate settings. This could facilitate pooled analyses linking viral genetic sequencing data to clinical severity, bringing insights to inform influenza surveillance and the vaccine strain selection process., Methods: We used a subset of data from the Global Influenza Hospital Surveillance Network database, including data from different geographical areas and income levels. To quantify the underlying concept of severity, an item response model was developed using 16 indicators of severity related to the hospital stay. Each patient in the dataset was assigned a Severity Score and a Severity Category (low, medium, or high severity). Finally, we compared the model scores across different subgroups., Results: Data from 9 countries were included, covering between 4 and 11 seasons from 2012 to 2022, with a total of 96,190 ARI hospitalizations. Not for all severity indicators data were available for all included seasons. Subgroups with a high percentage of patients in the high Severity Category included influenza A(H1N1)pdm09, age ≥ 50, lower-middle income countries, and admission since the start of the COVID-19 pandemic., Conclusions: The initial model successfully highlighted severity disparities across patient subgroups. Repeating this exercise with new, more complete data would allow recalibration and validation of the current model. The SevScale proved to be a promising method to define severity for influenza vaccine strain selection, surveillance, and research., (© 2025 The Author(s). Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

Background: Vaccination is a key measure in influenza control, yet global coverage rates remain low, although previous research reported an increase in influenza vaccination coverage rates (VCR) after the onset of the COVID-19 pandemic. This study aims to assess whether these changes were sustained over time by analyzing VCR trends from 2012 to 2023 in the countries included in the FluCov project., Methods: Data on influenza VCR from 2012 to 2023 for different age and risk groups were extracted from national health organizations and international sources for countries included in the FluCov project. For coverage rates in the older adults, segmented regression models were used to test if 2020 marked a significant change in VCR trends. Moreover, polynomial regression models were fitted for each country with VCR in the period 2012 to 2020 to predict coverage rates for 2021 to 2023 and to compare these to the actual coverage rates for 2021 to 2023., Results: For the elderly, we retrieved influenza VCR data for 12 countries. In 2020, VCR among elderly increased in 10 countries, but the increase was statistically significant in Spain and England only. Moreover, all countries except Spain reverted to levels within the confidence intervals of trends modeled using pre-2020 data., Conclusions: Although influenza VCR increased in 2020, these changes were statistically significant in only two out of 12 countries, and no consistent, sustained increase was observed afterward, except in Spain. The findings suggest the need for continuous monitoring of VCR and the implementation of strategies to promote and maintain high vaccination coverage rates., (© 2025 The Author(s). Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

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.)