Component-specific effectiveness of trivalent influenza vaccine as monitored through a sentinel surveillance network in Canada, 2006-2007.
BACKGROUND
Trivalent inactivated influenza vaccine (TIV) is reformulated annually to contain representative strains of 2 influenza A subtypes (H1N1 and H3N2) and 1 B lineage (Yamagata or Victoria). We describe a sentinel surveillance approach to link influenza variant detection with component-specific vaccine effectiveness (VE) estimation.


METHODS
The 2006-2007 TIV included A/NewCaledonia/20/1999(H1N1)-like, A/Wisconsin/67/2005(H3N2)-like, and B/Malaysia/2506/2004(Victoria)-like components. Included participants were individuals >or=9 years of age who presented within 1 week after influenza like illness onset to a sentinel physician between November 2006 and April 2007. Influenza was identified by real-time reverse-transcriptase polymerase chain reaction and/or culture. Isolates were characterized by hemagglutination inhibition assay (HI) and HA1 gene sequence. VE was estimated as 1-[odds ratio for influenza in vaccinated versus nonvaccinated persons].


RESULTS
A total of 841 participants contributed: 69 (8%) were >or=65 years of age; 166 (20%) received the 2006-2007 TIV. Influenza was detected in 337 subjects (40%), distributed as follows: A/H3N2, 242 (72%); A/H1N1, 55 (16%); and B, 36 (11%). All but 1 of the A/H1N1 isolates were well matched, half of A/H3N2 isolates were strain mismatched, and all B isolates were lineage-level mismatched to vaccine. Age-adjusted estimated VE for A/H1N1, A/H3N2, and B components was 92% (95% CI, 40%-91%), 41% (95% CI, 6%-63%), and 19% (95% CI, -112% to 69%), respectively, with an overall VE estimate of 47% (95% CI, 18%-65%). Restriction of the analysis to include only working-age adults resulted in lower VE estimates with wide confidence intervals but similar component-specific trends.


CONCLUSIONS
Sentinel surveillance provides a broad platform to link new variant detection and the composite of circulating viruses to annual monitoring of component-specific VE.
Skowronski
Danuta M
DM
British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada. danuta.skowronski@bccdc.ca
De Serres
Gaston
G
Dickinson
Jim
J
Petric
Martin
M
Mak
Annie
A
Fonseca
Kevin
K
Kwindt
Trijntje L
TL
Chan
Tracy
T
Bastien
Nathalie
N
Charest
Hugues
H
Li
Yan
Y
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002170:Canada / Q000453:epidemiology; D002648:Child; D005260:Female; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry / Q000235:genetics; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D053122:Influenza A Virus, H3N2 Subtype / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D009981:Influenza B virus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control* / Q000821:virology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018571:Sentinel Surveillance; D017422:Sequence Analysis, DNA; D015164:Vaccines, Inactivated / Q000008:administration & dosage* / Q000276:immunology; D055815:Young Adult
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated