Zelner J, et al. - Developing a Bayesian hierarchical model, researchers assessed the effects of sequential influenza A(H1N1)pdm09 vaccination on hemagglutination-inhibition antibody boosting and waning in a longitudinal cohort of older children and adults from 2011 to 2016, a period during which the A(H1N1)pdm09 vaccine strain did not change. They Analyzed antibody measurements from 2,057 serum specimens longitudinally collected from 388 individuals, identifying the increased rate of antibody waning with successive vaccination. However, they noted that the estimated antibody half-life was longer than a typical influenza season even among the most highly vaccinated. This supports vaccination at the earliest opportunity as supported by current recommendations. Findings suggest a possible variation in patterns of boosting and waning with the influenza A(H3N2) subtype which evolves more rapidly and has been most associated with reduced effectiveness following repeat vaccination.