Tick-Borne Encephalitis (TBE) Vaccination in Children: Advantage of the Rapid Immunization Schedule (i.e., days 0, 7, 21)

Abstract

Tick-borne encephalitis (TBE) is an important, vaccine-preventable arthropod-borne disease, causing severe illness in children too. In order to evaluate the immune response to different licensed primary immunization schedules, a total of 294 children aged 1 to 11 years of age were enrolled in a randomized, controlled, multi-center trial. The subjects were vaccinated with the pediatric formulation of a TBE vaccine (Encepur children) according to the conventional schedule (Group C; N=73, vaccination on days 0, 28 and 300), the modified conventional schedule (Group M; N=139, vaccination on days 0, 21 and 300), or the rapid schedule (Group R; N=82, vaccination on Days 0, 7 and 21). Antibody titers as measured by neutralization-test (NT) and ELISA were determined on Days 0, 42, 180, 300, and 321. The demographic data of the study groups were similar. Most subjects (97%-100%) reached an NT titer of at least 1:10 on Day 42. On Day 42, the highest NT geometric mean titers (GMTs) were reached in Group C. In Group C and Group M, titers declined up to Day 300. Until Day 300, the highest NT-GMTs were maintained in Group R, notably without a decline compared to Day 42. Group M reached titers similar to Group R on Day 42, but these titers declined by 50% up to Day 180. Similar to the NT, on Day 42 highest geometric mean concentrations (GMCs) as measured by ELISA across all groups were reached in Group C. In all groups, titers declined until Day 300. On Day 300, GMC ELISA of Group R was higher compared to Group C and Group M. To conclude, the rapid immunization schedule in children not only provides fast protection but also leads to stable titers as measured by NT for at least 300 days after vaccination.