title: Estimates of influenza vaccine effectiveness for 2007-2008 from Canada's sentinel surveillance system: cross-protection against major and minor variants.
abstract: OBJECTIVE
  To estimate influenza vaccine effectiveness (VE) for the 2007-2008 season and assess the sentinel surveillance system in Canada for monitoring virus evolution and impact on VE.
  
  
  METHODS
  Nasal/nasopharyngeal swabs and epidemiologic details were collected from patients presenting to a sentinel physician within 7 days of influenza-like illness onset. Cases tested positive for influenza A/B virus by real-time polymerase chain reaction; controls tested negative. Hemagglutination inhibition (HI) and gene sequencing explored virus relatedness to vaccine. VE was calculated as 1 minus the odds ratio for influenza in vaccinated versus nonvaccinated participants, with adjustment for confounders.
  
  
  RESULTS
  Of 1425 participants, 21% were vaccinated. Influenza virus was detected in 689 (48%), of which isolates from 663 were typed/subtyped: 189 (29%) were A/H1, 210 (32%) were A/H3, and 264 (40%) were B. Of A/H1N1 isolates, 6% showed minor HI antigenic mismatch to vaccine, with greater variation based on genetic identity. All A/H3N2 isolates showed moderate antigenic mismatch, and 98% of influenza B virus isolates showed major lineage-level mismatch to vaccine. Adjusted VE for A/H1N1, A/H3N2, and B components was 69% (95% confidence interval [CI], 44%-83%), 57% (95% CI, 32%-73%), and 55% (95% CI, 32%-70%), respectively, with an overall VE of 60% (95% CI, 45%-71%).
  
  
  CONCLUSIONS
  Detailed antigenic and genotypic analysis of influenza viruses was consistent with epidemiologic estimates of VE showing cross-protection. A routine sentinel surveillance system that combines detailed virus and VE monitoring annually, as modeled in Canada, may guide improved vaccine selection and protection.
authors.affiliation: British Columbia Centre for Disease Control, Canada.
authors.forename: Naveed Z
authors.initials: NZ
authors.lastname: Janjua
authors.forename: Danuta M
authors.initials: DM
authors.lastname: Skowronski
authors.forename: Gaston
authors.initials: G
authors.lastname: De Serres
authors.forename: Jim
authors.initials: J
authors.lastname: Dickinson
authors.forename: Natasha S
authors.initials: NS
authors.lastname: Crowcroft
authors.forename: Marsha
authors.initials: M
authors.lastname: Taylor
authors.forename: Anne-Luise
authors.initials: AL
authors.lastname: Winter
authors.forename: Travis S
authors.initials: TS
authors.lastname: Hottes
authors.forename: Kevin
authors.initials: K
authors.lastname: Fonseca
authors.forename: Hugues
authors.initials: H
authors.lastname: Charest
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Drews
authors.forename: Suzana
authors.initials: S
authors.lastname: Sabaiduc
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bastien
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Gardy
authors.forename: Martin
authors.initials: M
authors.lastname: Petric
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000956:Antigens, Viral / Q000032:analysis; D002170:Canada / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D056738:Cross Protection; D005260:Female; D005838:Genotype; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D009981:Influenza B virus / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009305:Nasopharynx / Q000821:virology; D009666:Nose / Q000821:virology; D060888:Real-Time Polymerase Chain Reaction; D018571:Sentinel Surveillance; D017422:Sequence Analysis, DNA; D055815:Young Adult
chemical_list: D000956:Antigens, Viral; D007252:Influenza Vaccines