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Single-Dose Hepatitis A Immunization: 7.5-Year Observational Pilot Study in Nicaraguan Children to Assess Protective Effectiveness and Humoral Immune Memory Response

Mayorga, Orlando ; Bühler, Silja ; Jaeger, Veronika K. ; Bally, Seraina ; Hatz, Christoph ; Frösner, Gert ; Protzer, Ulrike ; Van Damme, Pierre ; Egger, Matthias ; Herzog, Christian

In: The Journal of Infectious Diseases, 2016, vol. 214, no. 10, p. 1498-1506

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    Title
    • Single-Dose Hepatitis A Immunization: 7.5-Year Observational Pilot Study in Nicaraguan Children to Assess Protective Effectiveness and Humoral Immune Memory Response
    Author
    • Mayorga, Orlando. National Autonomous University, León, Nicaragua
    • Bühler, Silja. University of Zürich
    • Jaeger, Veronika K.. Basel University Hospital
    • Bally, Seraina. Swiss Tropical and Public Health Institute
    • Hatz, Christoph. University of Zürich
    • Frösner, Gert. Technical University of Munich/Helmholtz Zentrum München, Germany
    • Protzer, Ulrike. Technical University of Munich/Helmholtz Zentrum München, Germany
    • Van Damme, Pierre. University of Antwerp, Belgium
    • Egger, Matthias. University of Bern, Switzerland
    • Herzog, Christian. Swiss Tropical and Public Health Institute
    Document Type
    • Postprint
    Language
    • English
    Published in
    • The Journal of Infectious Diseases, 2016, vol. 214, no. 10, p. 1498-1506. Oxford University Press
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:331199
    Summary
    Background Universal 2-dose hepatitis A virus (HAV) vaccination of toddlers effectively controls hepatitis A. High vaccine costs, however, impede implementation in endemic countries. To test single-dose vaccination as a possible alternative, we initiated an observational, longitudinal study in Nicaragua, to assess protective effectiveness and—through challenge vaccination—humoral immune memory response. Methods After a 2003 serosurvey, 130 originally seronegative children received one dose of virosomal HAV vaccine in 2005, followed by yearly serological and clinical assessments until 2012. After 7.5 years, a vaccine booster was administered. Concurrent antibody screening of patients presenting with hepatitis symptoms documented persistent HAV circulation in the communities studied. Results Between serosurvey and vaccination, 25 children contracted hepatitis A subclinically (>8000 mIU/mL anti-HAV). In the remaining 105 children, immunization resulted in anti-HAV levels of 17-572 mIU/mL. Based on the ≥15% annual infection risk, an estimated 60% of children were exposed to HAV encounters during follow-up. No child presented with hepatitis symptoms. Serological breakthrough infection (7106 mIU/mL) was documented in 1 child, representing an estimated protective effectiveness of 98.3% (95% confidence interval, 87.9-99.8). Boosting elicited an average 29.7-fold increase of anti-HAV levels. Conclusions In children living in hyperendemic settings, a single dose of virosomal HAV vaccine is sufficient to activate immune memory and may provide long-term protection.