Protective effect of single-dose adjuvanted pandemic influenza vaccine in children.
BACKGROUND
During the first wave of A/California/7/2009(H1N1) influenza, high rates of hospitalization in children under 5 years were seen in many countries. Subsequent policies for vaccinating children varied in both type of vaccine and number of doses. In Canada, children 36 months to <10 years received a single dose of 0.25 ml of the GSK adjuvanted vaccine (Arepanrix) equivalent to 1.9 microg HA. Children 6 months to 35 months received two doses as did those 36-119 months with chronic medical conditions.


METHODS
We conducted a community-based case-control vaccine effectiveness (VE) review of children under 10 years with influenza like illness who were tested for H1N1 infection at the central provincial laboratory. Laboratory-confirmed influenza was the primary outcome, and vaccination status the primary exposure to assess VE after a single 0.25-ml dose.


RESULTS
If vaccination was designated to be effective after 14 days, no vaccinated child had laboratory-confirmed influenza compared to 38% of controls. The VE of 100% was statistically significant for children <10 years of age and <5 years considered separately. If vaccination was considered effective after 10 days, VE dropped to 96% overall but was statistically significant and over 90% in all age subgroups, including those under 36 months.


CONCLUSIONS
A single 0.25-ml dose of the GSK adjuvanted vaccine (Arepanrix) protects children against laboratory-confirmed pandemic influenza potentially avoiding any increased reactogenicity associated with second doses. Adjuvanted vaccines offer hope for improved seasonal vaccines in the future.
Van Buynder
P G
PG
New Brunswick Department of Health, Office of the Chief Medical Officer of Health (OCMOH), Fredericton, NB, Canada. pjvb@iinet.net.au
Dhaliwal
J K
JK
Van Buynder
J L
JL
Couturier
C
C
Minville-Leblanc
M
M
Garceau
R
R
Tremblay
F-W
FW
D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D058873:Pandemics; D016896:Treatment Outcome; D014611:Vaccination / Q000706:statistics & numerical data
D000276:Adjuvants, Immunologic; D007252:Influenza Vaccines