539. The effectiveness of trivalent inactivated influenza vaccine in children over six consecutive influenza seasons
Session: Poster Abstract Session: Influenza Vaccines
Friday, October 21, 2011
Room: Poster Hall B1
  • Sato 539 IDSA Poster .png (625.6 kB)
  • Background: Influenza contributes an annual excess number of hospitalizations and is an important cause of morbidity and mortality among young children. Although trivalent inactivated influenza vaccine (TIV) is the only prophylactic intervention available for all children in Japan the data of the effectiveness of TIV are limited. In this study, we estimated the effectiveness of two doses of TIV in infants and young children for the prevention of influenza associated illness and hospitalization.

    Methods: A prospective, non-randomized, observational study over six consecutive influenza seasons, 2002/2003 to 2007/2008, was performed in a small community, Japan. 14,788 children aged six months to five years observed through an influenza season. TIV was offered annually to all children with an overall acceptance of 52.9%. Influenza rapid diagnostic tests were performed on specimens from all children with febrile respiratory symptoms during each subsequent winter surveillance period. The efficacy of two doses of TIV was estimated by the relative risk of influenza confirmed illness and 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 proven influenza A, two doses of TIV showed yearly efficacies that ranged from 42% to 69% with the highest efficacy 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.

    Conclusion: This study demonstrates that TIV when given with high and sustained vaccine coverage in the setting of routine pediatric care is consistently effective at preventing influenza and resultant hospitalizations. It is encouraging that both that efficacy was greatest in the youngest studied (6-12 months) and that overall efficacy was greater in the prevention of hospitalization than overall respiratory illness.

    Subject Category: I. Adult and Pediatric Vaccines

    Masatoki Sato, MD1, Masahiko Katayose, MD2, Mitsuaki Hosoya, MD1, Takashi Haneda, MD3, Hideo Yamaguchi, MD4, Yukihiko Kawasaki, MD1 and Peter Wright, MD5, (1)Pediatrics, Fukushima Medical University, Fukushima, Japan, (2)Pediatrics, Soma General Hospital, Soma, Japan, (3)Haneda Clinic, Soma, Japan, (4)Yamaguchi Children's Clinic, Soma, Japan, (5)Pediatrics, Dartmouth Medical School, Lebanon, NH


    M. Sato, None

    M. Katayose, None

    M. Hosoya, None

    T. Haneda, None

    H. Yamaguchi, None

    Y. Kawasaki, None

    P. Wright, None

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