PLoS Medicine (Jan 2011)

Estimates of pandemic influenza vaccine effectiveness in Europe, 2009-2010: results of Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) multicentre case-control study.

  • Marta Valenciano,
  • Esther Kissling,
  • Jean-Marie Cohen,
  • Beatrix Oroszi,
  • Anne-Sophie Barret,
  • Caterina Rizzo,
  • Baltazar Nunes,
  • Daniela Pitigoi,
  • Amparro Larrauri Cámara,
  • Anne Mosnier,
  • Judith K Horvath,
  • Joan O'Donnell,
  • Antonino Bella,
  • Raquel Guiomar,
  • Emilia Lupulescu,
  • Camelia Savulescu,
  • Bruno C Ciancio,
  • Piotr Kramarz,
  • Alain Moren

DOI
https://doi.org/10.1371/journal.pmed.1000388
Journal volume & issue
Vol. 8, no. 1
p. e1000388

Abstract

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BackgroundA multicentre case-control study based on sentinel practitioner surveillance networks from seven European countries was undertaken to estimate the effectiveness of 2009-2010 pandemic and seasonal influenza vaccines against medically attended influenza-like illness (ILI) laboratory-confirmed as pandemic influenza A (H1N1) (pH1N1).Methods and findingsSentinel practitioners swabbed ILI patients using systematic sampling. We included in the study patients meeting the European ILI case definition with onset of symptoms >14 days after the start of national pandemic vaccination campaigns. We compared pH1N1 cases to influenza laboratory-negative controls. A valid vaccination corresponded to >14 days between receiving a dose of vaccine and symptom onset. We estimated pooled vaccine effectiveness (VE) as 1 minus the odds ratio with the study site as a fixed effect. Using logistic regression, we adjusted VE for potential confounding factors (age group, sex, month of onset, chronic diseases and related hospitalizations, smoking history, seasonal influenza vaccinations, practitioner visits in previous year). We conducted a complete case analysis excluding individuals with missing values and a multiple multivariate imputation to estimate missing values. The multivariate imputation (n = 2902) adjusted pandemic VE (PIVE) estimates were 71.9% (95% confidence interval [CI] 45.6-85.5) overall; 78.4% (95% CI 54.4-89.8) in patients ConclusionsOur results suggest good protection of the pandemic monovalent vaccine against medically attended pH1N1 and no effect of the 2009-2010 seasonal influenza vaccine. However, the late availability of the pandemic vaccine and subsequent limited coverage with this vaccine hampered our ability to study vaccine benefits during the outbreak period. Future studies should include estimation of the effectiveness of the new trivalent vaccine in the upcoming 2010-2011 season, when vaccination will occur before the influenza season starts.