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Title: Cross-protection elicited by primary and booster vaccinations against Japanese encephalitis: A two-year follow-up study
Authors: Elina O. Erra
Helena Hervius Askling
Sutee Yoksan
Lars Rombo
Jukka Riutta
Sirkka Vene
Lars Lindquist
Olli Vapalahti
Anu Kantele
University of Helsinki Haartman Institute
Helsinki University Hospital
Karolinska Institutet
Mahidol University
Sormland County Council
Medical Centre Aava
Swedish Institute for Communicable Disease Control
Helsingin Yliopisto
Keywords: Biochemistry, Genetics and Molecular Biology;Immunology and Microbiology;Medicine;Veterinary
Issue Date: 17-Dec-2013
Citation: Vaccine. Vol.32, No.1 (2013), 119-123
Abstract: Background: 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. Methods: 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. PRNT50titers≥10 were considered protective. Results: 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%. Conclusions: 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. © 2013 The Authors.
ISSN: 18732518
Appears in Collections:Scopus 2011-2015

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