Up to 10,000 cases of tick-borne encephalitis are registered annually, 20% of which occur in children under 17 years of age. A comparison of the immunogenicity and safety between a new pediatric Tick-E-Vac vaccine based on the tick-borne encephalitis virus (TBEV) strain Sofjin and FSME-IMMUN Junior vaccine was performed in the Sverdlovsk region. The vaccine strains differ from strains of the Siberian subtype of TBEV that dominates in the region.

The purpose of a recent study published in Advances in Virology was to compare the immunogenicity and safety of new pediatric Tick-E-Vac vaccines – based on the TBEV strain Sofjin and FSME-IMMUN Junior vaccine.

This study enrolled 163 children aged 1-15 years who received one of the vaccines—according to either a conventional or rapid vaccination schedule. Immunogenicity was assessed based on the seroprotection rates and titers of virus-neutralizing antibodies.

No significant differences were observed in either the immunogenicity or reactogenicity of the pediatric vaccines based on strains of the Far Eastern or European subtypes of TBEV. Under both vaccination schedules—30 days after the second injection—seroprotection rates were 100% for Tick-E-Vac and greater than 95% for FSME-IMMUN Junior. The geometric mean titer of TBEV-neutralizing antibodies was at least 2,4 log10 (1 : 250) for either vaccine. Whereas, 14 days after the second injection, seroprotection rates were significantly lower – ranging from 50-63% regardless of the vaccine used. The observed adverse reactions were mild or moderate for bothvaccines, under both vaccination schedules – with total adverse event rates being less than 25%. While the reactogenicity was not associated with the gender or age of recipients. There were no statistically significant differences in the incidence of adverse reactions between the group of subjects who were baseline seronegative or seropositive. However, 14 days after the second vaccine injection, a statistically significant difference in nAbs titers was identified between groups of children with and without reported reactions.

The results suggested acceptable reactogenicity and high immunogenicity of the pediatric form of Tick-E-Vac and FSME-IMMUN Junior. Under conventional and rapid vaccination schedules, in the thirty days after the second injection, the two-dose primary immunization induced protective titers of TBEV neutralizing antibodies in protective titers in at least 95% of vaccinated subjects.

Source: Advances in Virology. 2019 Dec 24;2019:5323428. doi: 10.1155/2019/5323428. eCollection 2019.