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Cross-protection elicited by primary and booster vaccinations against Japanese encephalitis: A two-year follow-up study
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centrum för klinisk forskning i Sörmland (CKFD).
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2013 (English)In: Vaccine, ISSN 0264-410X, E-ISSN 1873-2518, Vol. 32, no 1, 119-123 p.Article in journal (Refereed) Published
Abstract [en]


The inactivated Vero cell-derived vaccine (JE-VC, IXIARO) has replaced the traditional mouse brain-derived preparations (JE-MB) in travelers' vaccinations against Japanese encephalitis. We showed recently that a single JE-VC dose efficiently boosts immunity in JE-MB-primed vaccinees, and that JE-VC elicits cross-protective immunity against non-vaccine genotypes, including the emerging genotype I. While these studies only provided short-term data, the present investigation evaluates the longevity of seroprotection in the same volunteers.


The study comprised 48 travelers who had received (1) JE-VC primary series, (2) JE-MB primary series followed by a single JE-VC booster dose, or (3) JE-MB primary series and a single JE-MB booster dose. Serum samples were collected two years after the last vaccine dose, and evaluated with the plaque-reduction neutralization test against seven Japanese encephalitis virus strains representing genotypes I-IV. PRNT50 titers >= 10 were considered protective.


Two years after the primary series with JE-VC, 87-93% of the vaccinees proved to be cross-protected against test strains representing genotypes II-IV and 73% against those of genotype I. After a single homologous or heterologous booster dose to JE-MB-primed subjects, the two-year seroprotection rates against genotype I-IV strains were 89-100%.


After JE-VC primary series, seroprotection appeared to wane first against genotype I. The first booster should not be delayed beyond two years. In JE-MB-primed subjects, a single JE-VC booster provided cross-protective immunity against genotype I-IV strains in almost all vaccinees, suggesting an interval of two years or even longer for the second booster. These data further support the use of a single JE-VC dose for boosting JE-MB immunity.

Place, publisher, year, edition, pages
2013. Vol. 32, no 1, 119-123 p.
Keyword [en]
Japanese encephalitis, Vaccine, Cross-protection, Duration of protection, Booster, Ixiaro
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-218600DOI: 10.1016/j.vaccine.2013.10.055ISI: 000329684700020OAI: oai:DiVA.org:uu-218600DiVA: diva2:696182
Available from: 2014-02-13 Created: 2014-02-13 Last updated: 2014-02-13Bibliographically approved

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