Antigen dependent adverse reactions and seroconversion of a tick-borne encephalitis vaccine in children

Area of Science:

• Pediatrics
• Immunology
• Vaccinology

Background:

• Tick-borne encephalitis (TBE) is a significant viral infection transmitted by ticks, particularly prevalent in parts of Europe and Asia.
• Vaccination is the primary method for preventing TBE, but optimal dosing for pediatric populations requires further investigation.
• Existing TBE vaccines may contain albumin or thiomersal, necessitating the development of alternative formulations.

Purpose of the Study:

• To compare the efficacy and safety of two different doses of an albumin-free and thiomersal-free TBE vaccine in children.
• To evaluate the immune response and adverse events associated with full adult dose versus half adult dose TBE vaccination in pediatric subjects.
• To determine the recommended TBE vaccine dosage for children aged 1 to 12 years.

Main Methods:

• Two randomized, double-blind, dose-comparison studies were conducted.
• 595 children aged 6 months to 12 years were enrolled in Austria and Germany.
• Participants received either the full adult dose or half the adult dose of the TBE vaccine.

Main Results:

• An age-dependent immune response was observed in children under 1 year old.
• Fewer adverse systemic events, such as fever, were noted with the half-dose regimen.
• Seroconversion rates were comparable: 93% (half dose) vs. 98% (full dose) after the second vaccination, and 100% for both groups after the third vaccination.

Conclusions:

• The half adult dose of the TBE vaccine is recommended for children aged 1 to 12 years.
• This dosage provides comparable immunogenicity to the full adult dose with an improved safety profile.
• The albumin-free and thiomersal-free formulation offers a safer TBE vaccination option for pediatric populations.