Factors Associated with Pre-season Seroprotection to B Lineage Influenza Viruses in Children
Methods: Serum was drawn from 163 children prior to 2013-14 influenza vaccination, including 53 (33%) with PCR-confirmed B lineage infection in 2012-13, 91 (56%) who received the 2012-13 vaccine (Yamagata lineage) and 21 (13%) who were both vaccinated and infected. Antibody titers were measured by hemagglutination-inhibition (HI) assays for both influenza B lineage strains licensed for use in the 2013-14 vaccines. The association between seroprotective titer (≥1:40) and prior vaccine exposure or infection was examined in a modified Poisson regression model. Potential predictors included age, prior vaccine receipt, number of lineage specific vaccines received in the past 5 seasons, and lineage specific B infection in the prior season. Titers were analyzed separately for B/Yamagata and B/Victoria.
Results: Of 163 children, 96 (59%) had seroprotective titers for B/Victoria, 106 (65%) had seroprotective titers for B/Yamagata, and 73 (45%) had seroprotective titers for both viruses; 22 (13%) had been infected with B/Yamagata and 31 (19%) with B/Victoria in 2012-13. Vaccination in the 2012-13 season and ≥1 dose of B/Yamagata containing vaccine in the past 5 seasons were significantly associated with seroprotective titers for B/Yamagata in univariate analyses; prior infection was not significant. In the multivariate model, only 2012-13 vaccine receipt was significantly associated with a seroprotective titer for B/Yamagata (RR 1.5, 95%CI 1.2-1.9). A seroprotective titer for B/Victoria was independently associated with receipt of 2012-13 vaccine (RR 1.4, 95%CI 1.1-1.8) and with B/Victoria infection the 2012-13 season (RR 1.4, 95%CI 1.1-1.8) in the multivariate analysis.
Conclusion: Prior vaccine receipt is an important determinant of seroprotective titers for both B lineages in children. Prior receipt of B/Yamagata vaccine was associated with heterologous titers to B/Victoria.
M. Sundaram, MedImmune, LLC: Project scientist on MedImmune-funded grant, Research grant
J. Meece, None
S. Spencer, None
J. H. Kim, None
T. Friedrich, None
B. Flannery, None
A. M. Fry, None
E. Belongia, MedImmune, LLC: Grant Investigator, Research grant