Eurosurveillance, Volume 16, Issue 7, 17 February 2011
Surveillance and outbreak reports
Effectiveness of trivalent seasonal and monovalent influenza A(H1N1)2009 vaccines in population with major chronic conditions of Navarre, Spain: 2010/11 mid-season analysis
J Castilla (
)<sup>1</sup><sup>,2</sup>, J Mor?n<sup>3</sup>, V Mart?nez-Artola<sup>4</sup>, G Reina<sup>5</sup>, I Mart?nez-Baz<sup>1</sup><sup>,2</sup>, M Garc?a Cenoz<sup>1</sup><sup>,2</sup>, N Alvarez<sup>6</sup>, F Irisarri<sup>1</sup><sup>,2</sup>, M Arriazu<sup>1</sup><sup>,2</sup>, F El?a<sup>3</sup>, E Salcedo<sup>4</sup>
ii=19799. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19799
Date of submission: 03 February 2011 <hr class="Centre_divider">
We defined a cohort of people with major chronic conditions (152,585 subjects) in Navarre, Spain, using electronic records from physicians, to obtain 2010/11 mid-season estimates of influenza vaccine effectiveness. The adjusted estimates of the effectiveness of the 2010/11 trivalent influenza vaccine were 31% (95% confidence interval (CI): 20?40%) in preventing medically attended influenza-like illness, and 58% (95% CI: 11?80%) in preventing laboratory-confirmed influenza. Having received the monovalent influenza A(H1N1)2009 vaccine in the 2009/10 season had an independent preventive effect against medically attended influenza-like illness (17%, 95% CI: 1?30%), and having received both vaccines had 68% (95% CI: 23?87%) effectiveness in preventing laboratory-confirmed influenza.
<hr> Introduction
Because the influenza vaccine composition is adapted every season to the circulating viruses, its effectiveness varies. Estimates of the effectiveness of the vaccine during the influenza season help guiding health interventions aimed at reducing the impact of influenza in the population [1]. In the absence of randomised trials evaluating the efficacy of this vaccine, observational studies are of interest to verify if the expected effect has been achieved [1-3]. A multi-centre European study (I-MOVE: Influenza Monitoring Vaccine Effectiveness in Europe) was launched in 2008, including cohort and case-control studies in several settings. As part of this project, a cohort study is being conducted in Navarre, Spain [1].
During the early 2010/11 season, the influenza A(H1N1)2009 virus was the predominant circulating influenza virus [4]. It is therefore expected that both the trivalent 2010/11 seasonal vaccine, which includes this virus, [5] and the monovalent influenza A(H1N1)2009 vaccine [6] may provide some protection. Several studies have reported high effectiveness of the monovalent pandemic vaccine in preventing influenza A(H1N1)2009 during the 2009/10 season [7-11]. The aim of this study was to provide early estimates of the effectiveness of the 2010/11 seasonal vaccine and the influenza A(H1N1)2009 vaccine administered during the 2009/10 season in preventing medically attended influenza-like illness (MA-ILI) and laboratory-confirmed influenza during the 2010/11 season. The study was restricted to the population with major chronic conditions, since vaccination with both influenza vaccines was recommended for this group.
Surveillance and outbreak reports
Effectiveness of trivalent seasonal and monovalent influenza A(H1N1)2009 vaccines in population with major chronic conditions of Navarre, Spain: 2010/11 mid-season analysis
J Castilla (
- Instituto de Salud P?blica de Navarra (Public Health Institute of Navarre), Pamplona, Spain
- CIBER de Epidemiolog?a y Salud P?blica (Biomedical Research Network of Epidemiology and Public Health)
- Direcci?n de Atenci?n Primaria, Servicio Navarro de Salud (Primary Health Care Department), Pamplona, Spain
- Complejo Hospitalario de Navarra (Navarre Hospital Complex), Pamplona, Spain
- Cl?nica Universidad de Navarra (University Clinic of Navarra), Pamplona, Spain
- Servicio Navarro de Salud (Navarre Health Service), Pamplona, Spain
ii=19799. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19799 Date of submission: 03 February 2011 <hr class="Centre_divider">
We defined a cohort of people with major chronic conditions (152,585 subjects) in Navarre, Spain, using electronic records from physicians, to obtain 2010/11 mid-season estimates of influenza vaccine effectiveness. The adjusted estimates of the effectiveness of the 2010/11 trivalent influenza vaccine were 31% (95% confidence interval (CI): 20?40%) in preventing medically attended influenza-like illness, and 58% (95% CI: 11?80%) in preventing laboratory-confirmed influenza. Having received the monovalent influenza A(H1N1)2009 vaccine in the 2009/10 season had an independent preventive effect against medically attended influenza-like illness (17%, 95% CI: 1?30%), and having received both vaccines had 68% (95% CI: 23?87%) effectiveness in preventing laboratory-confirmed influenza.
<hr> Introduction
Because the influenza vaccine composition is adapted every season to the circulating viruses, its effectiveness varies. Estimates of the effectiveness of the vaccine during the influenza season help guiding health interventions aimed at reducing the impact of influenza in the population [1]. In the absence of randomised trials evaluating the efficacy of this vaccine, observational studies are of interest to verify if the expected effect has been achieved [1-3]. A multi-centre European study (I-MOVE: Influenza Monitoring Vaccine Effectiveness in Europe) was launched in 2008, including cohort and case-control studies in several settings. As part of this project, a cohort study is being conducted in Navarre, Spain [1].
During the early 2010/11 season, the influenza A(H1N1)2009 virus was the predominant circulating influenza virus [4]. It is therefore expected that both the trivalent 2010/11 seasonal vaccine, which includes this virus, [5] and the monovalent influenza A(H1N1)2009 vaccine [6] may provide some protection. Several studies have reported high effectiveness of the monovalent pandemic vaccine in preventing influenza A(H1N1)2009 during the 2009/10 season [7-11]. The aim of this study was to provide early estimates of the effectiveness of the 2010/11 seasonal vaccine and the influenza A(H1N1)2009 vaccine administered during the 2009/10 season in preventing medically attended influenza-like illness (MA-ILI) and laboratory-confirmed influenza during the 2010/11 season. The study was restricted to the population with major chronic conditions, since vaccination with both influenza vaccines was recommended for this group.
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