title: The effectiveness of trivalent inactivated influenza vaccine in children over six consecutive influenza seasons.
abstract: OBJECTIVE
  To estimate the effectiveness of two doses of trivalent inactivated influenza vaccine (TIV) over six consecutive influenza seasons in a small community in Japan.
  
  
  METHODS
  A prospective, non-randomized, observational study of TIV effectiveness was performed involving children aged 6 months to 6 years accessing pediatric services in Soma and Shinchi, Japan. The total number of children under observation was 14,788. Each fall from 2002 to 2007 TIV was offered to all children with an average uptake of 52.9%. Influenza rapid diagnostic tests were performed to all children with respiratory symptoms and a temperature >38°C during each surveillance period. The efficacy of two doses of TIV was estimated by the relative risk of influenza illness and influenza associated hospitalizations and effectiveness by reduction in all respiratory illness in vaccinated and unvaccinated children.
  
  
  RESULTS
  Influenza A occurred each year resulting in approximately one in five children in the unvaccinated group having an influenza A related clinic visit. For influenza A, two doses of TIV showed yearly efficacies that ranged from 42% to 69% with the highest efficacy during the 2002/2003 influenza season when the vaccine strains were well matched with the circulating viruses. The overall efficacy of two doses of TIV against influenza A and B associated illness was 52% and 59%, respectively. TIV also reduced the rate of the influenza associated hospitalizations attributable to both influenza A and B.
  
  
  CONCLUSIONS
  Vaccination with two doses of TIV was consistently effective in preventing influenza-associated clinic visits and hospitalizations.
authors.affiliation: Department of Pediatrics, Soma General Hospital, Soma 976-0011, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Katayose
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Hosoya
authors.forename: Takashi
authors.initials: T
authors.lastname: Haneda
authors.forename: Hideo
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Kawasaki
authors.forename: Masatoki
authors.initials: M
authors.lastname: Sato
authors.forename: Peter F
authors.initials: PF
authors.lastname: Wright
mesh_terms: D000367:Age Factors; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000276:immunology* / Q000627:therapeutic use; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology* / Q000517:prevention & control*; D007564:Japan / Q000453:epidemiology; D011446:Prospective Studies; D012621:Seasons; D015164:Vaccines, Inactivated / Q000276:immunology / Q000627:therapeutic use
chemical_list: D007252:Influenza Vaccines; D015164:Vaccines, Inactivated