title: Efficacy of inactivated vaccine in preventing antigenically drifted influenza type A and well-matched type B.
abstract: OBJECTIVE
  To evaluate the efficacy of currently used inactivated influenza vaccine during a severe epidemic caused by antigenically drifted influenza type A(H3N2) and well-matched type B viruses during the 1992-1993 season.
  
  
  METHODS
  Prospective nonrandomized controlled trial.
  
  
  METHODS
  An urban general hospital pediatric asthma clinic in Japan.
  
  
  METHODS
  A total of 137 children with moderate to severe asthma (mean age, 7.0 years; range, 2 to 14 years).
  
  
  METHODS
  Eighty-five children received trivalent split-antigen vaccine containing A/Beijing/352/89 (H3N2) and B/Bangkok/163/90 (B/Panama/45/90-like strain). Fifty-two were unvaccinated.
  
  
  METHODS
  Protection against infection was determined using hemagglutination inhibition test and virus isolation. Clinical efficacy was estimated based on febrile episodes with antibody rise or virus isolation.
  
  
  RESULTS
  Although marked antigenic drift in hemagglutinin was demonstrated in the epidemic virus (A/Beijing/32/92-like strain), the protection against influenza type A(H3N2) infection was 67.5% (P < .01). The protection against influenza type B infection was 43.7% (P < .01), although the epidemic influenza type B viruses were antigenically almost identical to the vaccine strain. Inactivated vaccine was not effective for protection against influenza type B infection in children younger than 7 years. High clinical effectiveness was demonstrated in children at least 7 years of age during the epidemic.
  
  
  CONCLUSIONS
  Our data suggest that current inactivated vaccine is highly effective for protection against influenza type A(H3N2) virus infection regardless of antigenic drift. In contrast, the protective efficacy obtained by vaccination may not be sufficient against influenza type B virus infection, and especially in young children, it does not offer protection.
authors.affiliation: Department of Pediatrics, Nippon Kokan Hospital, Kawasaki, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Sugaya
authors.forename: K
authors.initials: K
authors.lastname: Nerome
authors.forename: M
authors.initials: M
authors.lastname: Ishida
authors.forename: M
authors.initials: M
authors.lastname: Matsumoto
authors.forename: K
authors.initials: K
authors.lastname: Mitamura
authors.forename: M
authors.initials: M
authors.lastname: Nirasawa
mesh_terms: D000293:Adolescent; D000914:Antibodies, Viral / Q000096:biosynthesis / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D000940:Antigenic Variation / Q000276:immunology; D001249:Asthma / Q000276:immunology* / Q000821:virology; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D009980:Influenza A virus / Q000276:immunology* / Q000302:isolation & purification; D009981:Influenza B virus / Q000276:immunology* / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D007564:Japan / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D015164:Vaccines, Inactivated / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated