Beran et al.
Second five-year follow-up after booster vaccination against tick-borne encephalitis following different primary vaccination schedules demonstrates at least 10 years antibody persistence.
Vaccine 2019, 27: 4623-4629
In a clinical trial, for the TBE vaccine based on strain K23 (European subtype) using various primary immunization schedules in adolescents and adults (conventional, accelerated conventional, modified conventional and rapid), it had been shown that the antibodies persist at least for five years after the first booster dose. In an extension study, the antibody persistence was now evaluated from six up to ten years post-last vaccination. While the lowest limit of detection for neutralizing antibodies was a titer of 2, NT titers of at least 10 were considered a clinical meaningful threshold. Of 206 screened individuals, 201 were enrolled and 191 completed the study. At all timepoints, all individuals (with two exceptions) had a NT of ≥2 as well as ≥10. The percentage of participants with NT titers of ≥10 were ≥98% in the per-protocol set in each of the groups (15-49 years, ≥50 years, ≥60 years) and the percentage of vaccinees with NT titers ≥10 across all timepoints did not seem to differ with age. Overall, GMTs remained similar across groups. NT GMTs seemed to decrease with increasing age but remained similar within the same age strata at each timepoint. These results confirm the long-term persistence of immune response against the strain K23 based TBE virus vaccine following a booster dose and the antibody persistence was independent from the primary immunization schedule as measured by the participants with NT titers above a chosen clinically meaningful threshold.