Influenza A/subtype and B/lineage effectiveness estimates for the 2011-2012 trivalent vaccine: cross-season and cross-lineage protection with unchanged vaccine.
BACKGROUND
We estimate vaccine effectiveness (VE) against both influenza A/subtypes and B/lineages in Canada for the 2011-2012 trivalent inactivated influenza vaccine (TIV) with components entirely unchanged from the 2010-2011 TIV and in the context of phenotypic and genotypic characterization of circulating viruses.


METHODS
In a test-negative case-control study VE was estimated as [1-(adjusted)OddsRatio] × 100 for RT-PCR-confirmed influenza in vaccinated vs nonvaccinated participants. Viruses were characterized by hemagglutination inhibition (HI) and sequencing of antigenic sites of the hemagglutinin (HA) gene.


RESULTS
There were 1507 participants. VE against A(H1N1)pdm09 was 80% (95% confidence interval [CI], 52%-92%): circulating viruses were HI-characterized as vaccine-matched and bore just 2 aminoacid (AA) differences from vaccine. VE against A/H3N2 was 51% (95% CI, 10%-73%): circulating viruses were HI-characterized as vaccine-related but bore ≥11AA differences from vaccine. VE against influenza B was 51% (95% CI, 26%-67%) in total: 71% (95% CI, 40%-86%) for lineage-matched B/Victoria and 27% (95% CI, -21% to 56%) for lineage-mismatched B/Yamagata. For both influenza A and B types, VE was similar among recipients of either 2010-2011 or 2011-2012 TIV alone, higher when vaccinated both seasons.


CONCLUSIONS
Phenotypic and genotypic characterization of circulating and vaccine viruses enhances understanding of TIV performance, shown in 2011-2012 to be substantial against well-conserved A(H1N1)pdm09 and lineage-matched influenza B, suboptimal against genetic-variants of A/H3N2, and further reduced against lineage-mismatched influenza B. With unchanged vaccine components, protection may extend beyond a single season.
Danuta M
DM
Skowronski
Naveed Z
NZ
Janjua
Suzana
S
Sabaiduc
Gaston
G
De Serres
Anne-Luise
AL
Winter
Jonathan B
JB
Gubbay
James A
JA
Dickinson
Kevin
K
Fonseca
Hugues
H
Charest
Nathalie
N
Bastien
Yan
Y
Li
Trijntje L
TL
Kwindt
Salaheddin M
SM
Mahmud
Paul
P
Van Caeseele
Mel
M
Krajden
Martin
M
Petric
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000276:immunology; 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 / Q000276:immunology / Q000517:prevention & control* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D016896:Treatment Outcome; D014611:Vaccination / Q000379:methods*; D055815:Young Adult
D000956:Antigens, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines