Influenza vaccine effectiveness in preventing influenza A(H3N2)-related hospitalizations in adults targeted for vaccination by type of vaccine: a hospital-based test-negative study, 2011-2012 A(H3N2) predominant influenza season, Valencia, Spain.

PLoS ONE. 2014;9(11):e112294 DOI 10.1371/journal.pone.0112294


Journal Homepage

Journal Title: PLoS ONE

ISSN: 1932-6203 (Online)

Publisher: Public Library of Science (PLoS)

LCC Subject Category: Medicine | Science

Country of publisher: United States

Language of fulltext: English

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Joan Puig-Barberà
Juan García-de-Lomas
Javier Díez-Domingo
Alberto Arnedo-Pena
Montserrat Ruiz-García
Ramón Limón-Ramírez
Silvia Pérez-Vilar
José Luis Micó-Esparza
Miguel Tortajada-Girbés
Concha Carratalá-Munuera
Rosa Larrea-González
Juan Manuel Beltrán-Garrido
Maria Del Carmen Otero-Reigada
Joan Mollar-Maseres
Patricia Correcher-Medina
Germán Schwarz-Chavarri
Vicente Gil-Guillén
Valencia Hospital Network for the Study of Influenza and Respiratory Virus Disease


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Time From Submission to Publication: 24 weeks


Abstract | Full Text

Most evidence of the effectiveness of influenza vaccines comes from studies conducted in primary care, but less is known about their effectiveness in preventing serious complications. Here, we examined the influenza vaccine effectiveness (IVE) against hospitalization with PCR-confirmed influenza in the predominant A(H3N2) 2011-2012 influenza season.A hospital-based, test-negative study was conducted in nine hospitals in Valencia, Spain. All emergency admissions with a predefined subset of symptoms were eligible. We enrolled consenting adults age 18 and over, targeted for influenza vaccination because of comorbidity, with symptoms of influenza-like-illness within seven days of admission. We estimated IVE as (1-adjusted vaccination odds ratio)*100 after accounting for major confounders, calendar time and recruitment hospital.The subjects included 544 positive for influenza A(H3N2) and 1,370 negative for influenza admissions. Age was an IVE modifying factor. Regardless of vaccine administration, IVE was 72% (38 to 88%) in subjects aged under 65 and 21% (-5% to 40%) in subjects aged 65 and over. By type of vaccine, the IVE of classical intramuscular split-influenza vaccine, used in subjects 18 to 64, was 68% (12% to 88%). The IVE for intradermal and virosomal influenza vaccines, used in subjects aged 65 and over, was 39% (11% to 58%) and 16% (-39% to 49%), respectively.The split-influenza vaccine was effective in preventing influenza-associated hospitalizations in adults aged under 65. The intradermal vaccine was moderately effective in those aged 65 and over.