Persistence of the immune response after vaccination with the Japanese encephalitis vaccine, IXIARO® in healthy adults: A five year follow-up study

Vaccine. 2019 May 1;37(19):2529-2531. doi: 10.1016/j.vaccine.2019.03.030. Epub 2019 Apr 5.


Immunization with the Japanese encephalitis (JE) vaccine IXIARO® results in protective neutralizing antibody levels for one year. Since persistence of protective titer levels beyond one year was unknown, a 5 years follow-up study was conducted. Additionally, data were stratified to compare the persistence of protective neutralizing antibodies against JE in people with or without tick-borne encephalitis (TBE) vaccination. Four weeks after the primary series, the percentage of subjects with PRNT50 titer ≥1:10 in the intent-to-treat population was 99%; the rate after 5 years was 81.6%. By month 24, 36, 48 and 60, the percentages were still 90.7%, 91.7%, 90.1%, 85.9%, respectively in the population who had received TBE vaccine compared to 67.9%, 71.9%, 69.1%, 63.8% in the population who had not. No long-term safety concerns were identified. These data indicate that vaccination with IXIARO® is able to induce protective titers that persist up to 60 months after the primary immunization. Clinical trial registry number NCT00596102.

Keywords: IC51; IXIARO®; Immunogenicity; Japanese encephalitis; Safety; Seroprotection; Traveler.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antibodies, Neutralizing / immunology
  • Antibodies, Viral / immunology
  • Encephalitis Virus, Japanese / immunology*
  • Encephalitis, Japanese / immunology*
  • Encephalitis, Japanese / prevention & control*
  • Female
  • Follow-Up Studies
  • Humans
  • Immunity*
  • Japanese Encephalitis Vaccines / immunology*
  • Male
  • Middle Aged
  • Neutralization Tests
  • Seroconversion
  • Vaccination
  • Young Adult


  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Japanese Encephalitis Vaccines

Associated data