tetano
Editor, Senior Moderator
Expert Rev Vaccines
. 2026 Dec;25(1):2722420.
doi: 10.1080/14760584.2026.2722420. Epub 2026 Aug 27.
Diogo F P Marques 1 2 , Angela M C Rose 1 , Susana Monge 3 4 , Iván Martínez-Baz 5 , Marijke Reynders 6 , Róisín Duffy 7 , Sierk D Marbus 8 , Silvia Bino 9 , Petr Husa 10 , Ralf Dürrwald 11 , Liem Binh Luong Nguyen 12 13 14 , Goranka Petrović 15 , Beatrix Oroszi 16 , Antonino Bella 17 , Monika Kuliese 18 , Stephen Abela 19 , Iwona Paradowska-Stankiewicz 20 , Ausenda Machado 21 , Odette Popovici 22 , Chris Robertson 23 24 , Francisco Pozo 25 26 , Ana S Lameiras Azevedo 27 , Camino Trobajo-Sanmartín 5 , Anna Parys 28 , Lisa Domegan 7 , Arianne B van Gageldonk-Lafeber 8 , Lenka Součková 10 , Kristin Tolksdorf 29 , Odile Launay 12 13 14 , Vesna Višekruna Vučina 15 , Gergő Túri 16 , Flavia Riccardo 17 , Ligita Jančorienė 30 , John Paul Cauchi 19 31 , Verónica Gómez 21 , Mihaela Lazar 32 , Jim McMenamin 23 33 , Baltazar Nunes 1 2
Affiliations
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.
Keywords: Human influenza; cohort studies; in-hospital mortality; influenza vaccine; intensive care units; multicenter studies; relative risk.
Older adults hospitalized with influenza may experience severe outcomes, such as admission to an intensive care unit (ICU) or death during their hospital stay. While influenza vaccines are known to reduce the risk of hospitalization, it is less clear whether they also reduce the risk of these severe outcomes once someone is already hospitalized. We analyzed data from a large European hospital network that collected information over several influenza seasons between 2015 and 2025. The study included 4,257 adults aged 65 years and older who were admitted to hospital and tested positive for influenza virus. We compared the risk of severe outcomes between vaccinated and unvaccinated people. Among vaccinated people positive for influenza virus, about 3 in 100 were admitted to an ICU, compared with about 5 in 100 unvaccinated people. Death in hospital occurred in about 5 in 100 people in both groups. After taking age, sex, long-term health conditions, timing of admission, season and study site into account, vaccination showed little or no clear association with ICU admission. In contrast, vaccinated individuals had a lower risk of dying in hospital than unvaccinated individuals. This corresponded to about a one-quarter reduction in the risk of death. This finding suggests that influenza vaccination may provide additional benefits in reducing the risk of death among older adults who are hospitalized with influenza, even when hospital admission is not prevented, supporting continued efforts to improve vaccine uptake in this high-risk population.
. 2026 Dec;25(1):2722420.
doi: 10.1080/14760584.2026.2722420. Epub 2026 Aug 27.
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
Diogo F P Marques 1 2 , Angela M C Rose 1 , Susana Monge 3 4 , Iván Martínez-Baz 5 , Marijke Reynders 6 , Róisín Duffy 7 , Sierk D Marbus 8 , Silvia Bino 9 , Petr Husa 10 , Ralf Dürrwald 11 , Liem Binh Luong Nguyen 12 13 14 , Goranka Petrović 15 , Beatrix Oroszi 16 , Antonino Bella 17 , Monika Kuliese 18 , Stephen Abela 19 , Iwona Paradowska-Stankiewicz 20 , Ausenda Machado 21 , Odette Popovici 22 , Chris Robertson 23 24 , Francisco Pozo 25 26 , Ana S Lameiras Azevedo 27 , Camino Trobajo-Sanmartín 5 , Anna Parys 28 , Lisa Domegan 7 , Arianne B van Gageldonk-Lafeber 8 , Lenka Součková 10 , Kristin Tolksdorf 29 , Odile Launay 12 13 14 , Vesna Višekruna Vučina 15 , Gergő Túri 16 , Flavia Riccardo 17 , Ligita Jančorienė 30 , John Paul Cauchi 19 31 , Verónica Gómez 21 , Mihaela Lazar 32 , Jim McMenamin 23 33 , Baltazar Nunes 1 2
Affiliations
- PMID: 42657682
- DOI: 10.1080/14760584.2026.2722420
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.
Keywords: Human influenza; cohort studies; in-hospital mortality; influenza vaccine; intensive care units; multicenter studies; relative risk.
Plain language summary
Older adults hospitalized with influenza may experience severe outcomes, such as admission to an intensive care unit (ICU) or death during their hospital stay. While influenza vaccines are known to reduce the risk of hospitalization, it is less clear whether they also reduce the risk of these severe outcomes once someone is already hospitalized. We analyzed data from a large European hospital network that collected information over several influenza seasons between 2015 and 2025. The study included 4,257 adults aged 65 years and older who were admitted to hospital and tested positive for influenza virus. We compared the risk of severe outcomes between vaccinated and unvaccinated people. Among vaccinated people positive for influenza virus, about 3 in 100 were admitted to an ICU, compared with about 5 in 100 unvaccinated people. Death in hospital occurred in about 5 in 100 people in both groups. After taking age, sex, long-term health conditions, timing of admission, season and study site into account, vaccination showed little or no clear association with ICU admission. In contrast, vaccinated individuals had a lower risk of dying in hospital than unvaccinated individuals. This corresponded to about a one-quarter reduction in the risk of death. This finding suggests that influenza vaccination may provide additional benefits in reducing the risk of death among older adults who are hospitalized with influenza, even when hospital admission is not prevented, supporting continued efforts to improve vaccine uptake in this high-risk population.