Safety, immunogenicity and tolerability of a new pediatric tick-borne encephalitis (TBE) vaccine, free of protein-derived stabilizer

A total of 3559 children aged 1–11 years were enrolled in two clinical studies to evaluate immunogenicity and safety of a new pediatric tick-borne encephalitis (TBE) vaccine, free of protein-derived stabilizer. Immunogenicity was evaluated in the rapid immunization schedule (Days 0, 7, and 21) from sera collected at baseline and on Day 42 post-immunization by in vitro TBE virus neutralization test. All subjects analyzed achieved levels of TBE antibodies to fulfil the definition of seroconversion or a four-fold increase in antibody titres from baseline. The frequency of solicited post-immunization reactions ranged from 1 to 32% for reported local reactions and from 1 to 14% for systemic reactions. Overall, this can be regarded as expected for an inactivated, aluminium-adjuvanted, TBE vaccine. There was no indication for any new safety issues. An acceptably low number of febrile reactions above 38°C with the highest frequency after first immunization (i.e. 15% and 5% in children aged 1–2 and 3–11 years, respectively), mainly below 39°C, was reported. The results of both studies clearly show that TBE vaccination with this new TBE vaccine formulation can be achieved with a high degree of safety in children from 1 to 11 years of age.