Repeated influenza vaccination for preventing severe and fatal influenza infection in older adults: A multicentre case-control study

Itziar Casado, Ángela Domínguez, Diana Toledo, Judith Chamorro, Jenaro Astray, Mikel Egurrola, María Amelia Fernández-Sierra, Vicente Martín, María Morales-Suárez-Varela, Pere Godoy, Jesús Castilla, J. M. Mayoral, J. Díaz-Borrego, A. Morillo, M. J. Pérez-Lozano, J. Gutiérrez, M. Pérez-Ruiz, S. Tamames, S. Rojo-Rello, R. Ortiz De LejarazuM. I. Fernández-Natal, T. Fernández-Villa, A. Pueyo, A. Vilella, M. Campins, A. Antón, G. Navarro, M. Riera, E. Espejo, M. D. Mas, R. Pérez, J. A. Cayla, C. Rius, N. Torner, C. Izquierdo, R. Torra, L. Force, N. Soldevila, I. Crespo, F. Sanz, M. F. Domínguez-Berjon, M. A. Gutiérrez, S. Jiménez, E. Gil, F. Martín, R. Génova-Maleras, M. C. Prados, F. Enzzine De Blas, M. A. Salvador, S. Rodríguez, M. Romero, J. C. Galán, E. Navas, L. Rodríguez, C. J. Álvarez, E. Banderas, S. Fernández, M. J. López De Goicoechea, J. Díaz-González

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18 Citations (Scopus)

Abstract

© 2018 Joule Inc. or its licensors. BACKGROUND: The effectiveness of repeated vaccination for influenza to prevent severe cases remains unclear. We evaluated the effectiveness of influenza vaccination on preventing admissions to hospital for influenza and reducing disease severity. METHODS: We conducted a case-control study in 20 hospitals in Spain during the 2013/14 and 2014/15 influenza seasons. Community-dwelling adults aged 65 years or older who were admitted to hospital for laboratory-confirmed influenza were matched with inpatient controls by sex, age, hospital and admission date. The effectiveness of vaccination in the current and 3 previous seasons in preventing influenza was estimated for inpatients with nonsevere influenza and for those with severe influenza who were admitted to intensive care units (ICUs) or who died. RESULTS: We enrolled 130 inpatients with severe and 598 with nonsevere influenza who were matched to 333 and 1493 controls, respectively. Compared with patients who were unvaccinated in the current and 3 previous seasons, adjusted effectiveness of influenza vaccination in the current and any previous season was 31% (95% confidence interval [CI] 13%-46%) in preventing admission to hospital for nonsevere influenza, 74% (95% CI 42%-88%) in preventing admissions to ICU and 70% (95% CI 34%-87%) in preventing death. Vaccination in the current season only had no significant effect on cases of severe influenza. Among inpatients with influenza, vaccination in the current and any previous season reduced the risk of severe outcomes (adjusted odds ratio 0.45, 95% CI 0.26-0.76). INTERPRETATION: Among older adults, repeated vaccination for influenza was twice as effective in preventing severe influenza compared with nonsevere influenza in patients who were admitted to hospital, which is attributable to the combination of the number of admissions to hospital for influenza that were prevented and reduced disease severity. These results reinforce recommendations for annual vaccination for influenza in older adults.
Original languageEnglish
Pages (from-to)E3-E12
JournalCMAJ
Volume190
Issue number1
DOIs
Publication statusPublished - 8 Jan 2018

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