title: Serological response to influenza vaccination among children vaccinated for multiple influenza seasons.
abstract: BACKGROUND
  To evaluate if, among children aged 3 to 15 years, influenza vaccination for multiple seasons affects the proportion sero-protected.
  
  
  RESULTS
  Participants were 131 healthy children aged 3-15 years. Participants were vaccinated with trivalent inactivated seasonal influenza vaccine (TIV) over the 2005-06, 2006-07 and 2007-8 seasons. Number of seasons vaccinated were categorized as one (2007-08); two (2007-08 and 2006-07 or 2007-08 and 2005-06) or three (2005-06, 2006-07, and 2007-08). Pre- and post-vaccination sera were collected four weeks apart. Antibody titres were determined by hemagglutination inhibition (HAI) assay using antigens to A/Solomon Islands/03/06 (H1N1), A/Wisconsin/67/05 (H3N2) and B/Malaysia/2506/04. The proportions sero-protected were compared by number of seasons vaccinated using cut-points for seroprotection of 1:40 vs. 1:320. The proportions of children sero-protected against H1N1 and H3N2 was high (>85%) regardless of number of seasons vaccinated and regardless of cut-point for seroprotection. For B Malaysia there was no change in proportions sero-protected by number of seasons vaccinated; however the proportions protected were lower than for H1N1 and H3N2, and there was a lower proportion sero-protected when the higher, compared to lower, cut-point was used for sero-protection.
  
  
  CONCLUSIONS
  The proportion of children sero-protected is not affected by number of seasons vaccinated.
authors.affiliation: Department of Pathology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Sajjad
authors.initials: S
authors.lastname: Rafiq
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Russell
authors.forename: Richard
authors.initials: R
authors.lastname: Webby
authors.forename: Kevin
authors.initials: K
authors.lastname: Fonseca
authors.forename: Marek
authors.initials: M
authors.lastname: Smieja
authors.forename: Pardeep
authors.initials: P
authors.lastname: Singh
authors.forename: Mark
authors.initials: M
authors.lastname: Loeb
mesh_terms: D000293:Adolescent; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control / Q000821:virology; D008297:Male; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines