title: Protective effects of influenza A (H1N1) pandemic 2009 vaccination against the onset of influenza-like illness and asthma exacerbation in Japanese children.
abstract: BACKGROUND
  Vaccination against influenza A(H1N1)pdm09 in Japan started in October 2009. Children with asthma are considered as a high-risk group and are recommended to preferentially receive the vaccine.
  
  
  OBJECTIVE
  To identify the clinical effects of vaccination in Japanese children with and without asthma.
  
  
  METHODS
  We conducted a cross-sectional, questionnaire-based survey to compare vaccination rates, vaccine effectiveness against physician-diagnosed influenza A infection (PDIA), and consecutive asthma exacerbations between children with and without asthma.
  
  
  RESULTS
  Of the 460 children included in this study, those with asthma had higher vaccination rates (46.5%, 67/144) than those without asthma (30.4%, 96/316). Influenza A infections were diagnosed in 28 of 163 vaccinated children (17.2%) compared to 164 of 297 unvaccinated children (55.2%, p < 0.001). Comparison of positive influenza diagnosis rates between vaccinated and unvaccinated children with and without asthma showed that unvaccinated children with asthma had an elevated odds ratio (13.235; 95% confidence interval [CI], 5.564-32.134) and that treatment for asthma exacerbations was needed in a larger proportion of unvaccinated children. Vaccine effectiveness against PDIA was 87% (95% CI, 78-93%) overall, 92% (95% CI, 81-96%) in children with asthma and 81% (95% CI, 63-91%) in children without asthma, respectively.
  
  
  CONCLUSIONS
  The administration of an inactivated, split-virus, non-adjuvanted monovalent A(H1N1)pdm09 vaccine during the pandemic period reduced the number of physician-diagnosed influenza A infections and asthma exacerbations in children with asthma. Therefore, we strongly recommend that high-risk children with a history of asthma receive vaccines during pandemics.
authors.affiliation: Department of Pediatrics, Disaster Medical Center , Tokyo , Japan .
authors.forename: Yukako
authors.initials: Y
authors.lastname: Yokouchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Katsumori
authors.forename: Seigo
authors.initials: S
authors.lastname: Shirakawa
authors.forename: Maya
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kashima
authors.forename: Ryo
authors.initials: R
authors.lastname: Kozawa
authors.forename: Yuji
authors.initials: Y
authors.lastname: Koike
mesh_terms: D001249:Asthma / Q000150:complications*; D002648:Child; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000517:prevention & control*; D007564:Japan / Q000453:epidemiology; D008297:Male; D058873:Pandemics / Q000517:prevention & control; D011795:Surveys and Questionnaires
chemical_list: D007252:Influenza Vaccines
keywords: Asthmatic; high-risk group; pandemic; pediatrics; vaccine