LAIV effective in children despite prior vaccination

VANCOUVER, British Columbia — Recent study results suggested that vaccine efficacy may be lower among patients vaccinated in the prior season; however, data presented here at the 2014 Pediatric Academic Societies Annual Meeting showed otherwise.

Among children, influenza vaccine efficacy was consistently higher the second year of vaccination, regardless of whether vaccine strains were the same or different.

Herve Caspard, MD, of MedImmune, and colleagues conducted four randomized trials in which children aged 6 to 83 months received two doses of live-attenuated influenza vaccine each year for 2 years (n=2,497) or a placebo (n=1,648).

H1N1 vaccine strains were the same in three of the four trials. Consolidated vaccine efficacy for H1N1 was 89% in year 1 and 93% in year 2. When H1N1 vaccine strains differed between year 1 and 2, no cases of laboratory-confirmed H1N1 occurred in year 2.

H3N2 vaccine strains were the same in year 1 and 2 in one of the four trials. Among the three studies in which H3N2 vaccine strains were different between years, vaccine efficacy was 73% in year 1 and 88% in year 2.

Regarding influenza B, two trials included the same vaccine strains during study years. The vaccine was 89% effective in year 1 and 100% effective in year 2. Among the two studies in which influenza B vaccine strains differed, vaccine efficacy significantly differed (82% vs. –102%).

“When LAIV consolidated [vaccine efficacy] could be computed for year 2, they were consistently greater than 80%, regardless of whether vaccine strains in year 1 and 2 were the same or different. These data suggest that LAIV efficacy in children does not decline with revaccination,” researchers concluded.

For more information:

Caspard H. Abstract 3810.221. Presented at: PAS 2014; May 2-6, 2014; Vancouver, British Columbia.

Disclosure: The study was funded by MedImmune. All authors report financial ties with MedImmune.