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

摘要

Background: 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, man-ufactured by Bavarian Nordic, previously by GSK). Methods: 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 mean-ingful threshold and surrogate for protection. Results: 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 geo-metric mean titers also remained high among participants >= 50 years old (98-206) and >= 60 years old (91-191) across study groups and time points. Conclusions: 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 vaccina-tion schedule was given to adolescents or adults. Trial registry: ClinicalTrials.gov: NCT03294135. (c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).