Two doses of flu vaccine may enhance immunogenicity in infants

According to a randomized controlled trial reported online July 18 in Pediatrics, the administration of two full trivalent inactivated influenza vaccine doses to infants may enhance immunogenicity without increasing reactogenicity.
The primary immunogenicity outcome of the study was superiority of the full versus the half-dose, defined as at least a 10 percent increase in rates of seroprotection. The primary reactogenicity outcome was a fever within three days of either injection, Medscape reports.
"Infants and toddlers aged six to 23 months experience high rates of influenza hospitalization, highest in those younger than one year," Danuta M. Skowronski, of the British Columbia Center for Disease Control in Vancouver, Canada, said in the report, according to Medscape. "In North America, they are recommended to receive influenza vaccine annually at a per-injection dose half that recommended for older children and adults.... We assessed whether two full versus two half-doses of ...TIV could improve immunogenicity without increasing reactogenicity in infants (aged six to 11 months) and toddlers (aged 12 to 23 months)."
Of 252 participants included in per-protocol analyses, 128 were randomly assigned a half-dose and 124 were given a full-dose. After the immunization, seroprotection rates in toddlers exceeded 85 percent for all three vaccine components. There was no significant difference based on dose. Infants had higher responses with the full dose for all three vaccine components.  
"Administration of two full TIV doses may improve immunogenicity without increasing reactogenicity in infants," the study authors wrote, according to Medscape. "Current TIV dosing recommendations for young children warrant additional evaluation. Although cost-effectiveness analyses are needed, the incremental cost associated with full dosing would be limited to that of the vaccine itself because such a program change would not require an additional medical visit. Additional studies are needed to confirm these findings in a larger sample, with additional seasons' products, further age stratification, and with longer follow-up to assess antibody duration. Relevance to pandemic as well as seasonal vaccine recommendations should be assessed."