Taucher C, et al. - Researchers conducted this 5-year follow-up study to investigate if protective titer levels persisted beyond one year after immunization with the Japanese encephalitis (JE) vaccine IXIARO in healthy adults. They also compared the persistence of protective neutralizing antibodies against JE in those with or without tick-borne encephalitis (TBE) vaccination by stratifying the data. In the intent-to-treat population, the percentage of patients with PRNT50 titer ≥1:10 was 99% four weeks following the primary series; the rate was 81.6% after 5 years. In the population who had received TBE vaccine, the observed percentages by month 24, 36, 48 and 60 were still 90.7%, 91.7%, 90.1%, 85.9%, respectively; percentages were 67.9%, 71.9%, 69.1%, 63.8%, respectively, in the population who had not. There were no long-term safety concerns. Findings revealed that after the primary immunization, protective titers induced by vaccination with IXIARO persisted up to 60 months.