In children, the live-attenuated Japanese encephalitis chimeric virus vaccination JE-CV (IMOJEV®, Sanofi Pasteur) generates a strong antibody response that fades with time. Clinical effectiveness is based on a measure of protection against JE infection defined as neutralizing antibody levels equal to or greater than the 10 (1/dil) threshold. It is necessary to collect data on the length of persistence of the JE antibody response over this level. Researchers built statistical models utilizing 5-year persistence data from a randomized clinical trial (NCT00621764) in children primed with inactivated JE vaccine and given a booster dose of JE-CV, as well as in JE-naive toddlers (12-24 months) given a JE-CV single dose primary immunization. The models were built with OpenBugs V3.2.1 and implemented using a Bayesian Monte-Carlo Markov Chain method. Antibody persistence after JE-CV immunization was projected to last up to ten years. The results of a piecewise model with two phases (children) as well as a standard linear model (in the case of toddlers) are provided.
Expected median antibody titers (77 [2.5th–97.5th percentile range 41–144] 1/dil) in children remained above the threshold for seroprotection for more than 10 years after booster JE-CV immunization; the predicted median duration of protection was 19.5 years. Ten years following JE-CV main vaccination, median antibody titers in toddlers were anticipated to fall to roughly the level necessary for seroprotection (10.8 [5.8–20.1] 1/dil). A booster dosage of JE-CV in children is expected to give long-term JE protection. Such information can help with decision-making and suggestions for future immunization efforts.