Association between influenza vaccination and severe outcomes in adults aged ≥ 65 years hospitalized with laboratory-confirmed influenza : a retrospective cohort study, I-MOVE hospital network, Europe, 2015/16–2024/25

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Marques, Diogo F.P. and Rose, Angela M.C. and Monge, Susana and Martínez-Baz, Iván and Reynders, Marijke and Duffy, Róisín and Marbus, Sierk D. and Bino, Silvia and Husa, Petr and Dürrwald, Ralf and Luong Nguyen, Liem Binh and Petrović, Goranka and Oroszi, Beatrix and Bella, Antonino and Kuliese, Monika and Abela, Stephen and Paradowska-Stankiewicz, Iwona and Machado, Ausenda and Popovici, Odette and Robertson, Chris and Pozo, Francisco and Lameiras Azevedo, Ana S. and Trobajo-Sanmartín, Camino and Parys, Anna and Domegan, Lisa and van Gageldonk-Lafeber, Arianne B. and Součková, Lenka and Tolksdorf, Kristin and Launay, Odile and Višekruna Vučina, Vesna and Túri, Gergő and Riccardo, Flavia and Jančorienė, Ligita and Cauchi, John Paul and Gómez, Verónica and Lazar, Mihaela and McMenamin, Jim and Nunes, Baltazar (2026) Association between influenza vaccination and severe outcomes in adults aged ≥ 65 years hospitalized with laboratory-confirmed influenza : a retrospective cohort study, I-MOVE hospital network, Europe, 2015/16–2024/25. Expert Review of Vaccines, 25 (1). 2722420. ISSN 1476-0584 (https://doi.org/10.1080/14760584.2026.2722420)

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Abstract

Introduction: Older adults face an increased risk of influenza-related intensive care unit (ICU) admission and in-hospital death (IHD). Although vaccination reduces hospitalization, its effect on these outcomes remains uncertain. We estimated the association between influenza vaccination and both outcomes among adults aged ≥65 years hospitalized with laboratory-confirmed influenza. Research design and methods: We conducted a retrospective cohort study using European I-MOVE hospital network data (2015/16–2024/25); vaccination was defined as vaccine receipt ≥14 days before symptom onset. We estimated pooled-season adjusted risk ratios (aRR) using Poisson regression adjusting for potential confounders. We calculated relative risk reduction (RRR) as (1−aRR)×100, overall and by age group (65–79, ≥80 years). Results: After exclusions, 4,257 patients (five study sites, six seasons) were included. ICU admission occurred in 3% of vaccinated and 5% of unvaccinated patients; IHD occurred in 5% of both groups. RRR was 11% (95% CI: −21–34) against ICU admission (65–79 years: −4%; ≥80 years: 44%). RRR against IHD was 26% (95% CI: 3–43); 17% and 29% in each respective age group. Conclusions: Vaccination showed little or no association with ICU admission, but was associated with a one-quarter reduction in IHD among hospitalized older adults, reinforcing its benefits against fatal in-hospital outcomes.

ORCID iDs

Marques, Diogo F.P., Rose, Angela M.C., Monge, Susana, Martínez-Baz, Iván, Reynders, Marijke, Duffy, Róisín, Marbus, Sierk D., Bino, Silvia, Husa, Petr, Dürrwald, Ralf, Luong Nguyen, Liem Binh, Petrović, Goranka, Oroszi, Beatrix, Bella, Antonino, Kuliese, Monika, Abela, Stephen, Paradowska-Stankiewicz, Iwona, Machado, Ausenda, Popovici, Odette, Robertson, Chris ORCID logoORCID: https://orcid.org/0000-0001-6848-5241, Pozo, Francisco, Lameiras Azevedo, Ana S., Trobajo-Sanmartín, Camino, Parys, Anna, Domegan, Lisa, van Gageldonk-Lafeber, Arianne B., Součková, Lenka, Tolksdorf, Kristin, Launay, Odile, Višekruna Vučina, Vesna, Túri, Gergő, Riccardo, Flavia, Jančorienė, Ligita, Cauchi, John Paul, Gómez, Verónica, Lazar, Mihaela, McMenamin, Jim and Nunes, Baltazar;
CORE (COnnecting REpositories)