Sustained antibody persistence for at least 15 years after a booster vaccination against tick-borne encephalitis following different primary vaccination schedules: Third 5-year follow-up.

• Tick-borne encephalitis (TBE) virus can cause severe illness and neurological sequelae. • The best protection against TBE is prevention through vaccination. • Duration of protection after TBE vaccination is not known. • We showed antibody persistence for at least 15 years after TBE vaccine booster vaccination. • Antibody persistence was similar for the three licensed TBE vaccine primary schedules in all age groups included in this study. Vaccination is the best mode of protection against tick-borne encephalitis (TBE) and its sequelae. The duration of protection and the optimal interval of repeat booster doses are still debated. The current study evaluated the persistence of the antibody response 11–15 years after a first booster vaccination following different primary vaccination schedules with a TBE vaccine (Encepur Adults , manufactured by Bavarian Nordic, previously by GSK). This phase IV, open-label, mono-centric extension study enrolled adults who had received (at ≥ 12 years of age) primary vaccination with one of three randomly assigned TBE vaccine schedules (rapid [group R], conventional [group C], or accelerated conventional schedule [group A]) followed by a booster dose 3 years later. The antibody response was measured annually from 11 to 15 years post-booster using a TBE virus neutralization test (NT). An NT titer of ≥ 10 was considered as a clinically meaningful threshold and surrogate for protection. In total, 194 participants were enrolled and included in the per-protocol set; 188 completed the study. The percentage of participants with an NT titer ≥ 10 was 100% in group R and 99.0% in group A at all visits and ranged from 100% (year 11) to 95.8% (year 15) in group C. NT geometric mean titers were similar in the three study groups (181–267 in group R, 142–227 in group C, 141–209 in group A). NT geometric mean titers also remained high among participants ≥ 50 years old (98–206) and ≥ 60 years old (91–191) across study groups and time points. This study showed neutralizing antibody persistence for at least 15 years after a first booster dose of the Encepur Adults TBE vaccine in all age groups evaluated, regardless of which primary vaccination schedule was given to adolescents or adults. Trial registry : ClinicalTrials.gov : NCT03294135. [ABSTRACT FROM AUTHOR]