Changes in the epidemiology of hepatitis A outbreaks 13 years after the introduction of a mass vaccination program

Ana Martínez, Sonia Broner, M. Rosa Sala, Sandra Manzanares-Laya, Pere Godoy, Caritat Planas, Sofia Minguell, Nuria Torner, Mireia Jané, Angela Domínguez, M. Alsedà, C. Arias, I. Barrabeig, N. Camps, M. Carol, M. Company, J. Ferràs, G. Ferrús, I. Parrón, A. RoviraR. Torras, P. Olalla, J. Caylà

Research output: Contribution to journalArticlepeer-review

Abstract

A hepatitis A+B vaccine vaccination program of 12-year-olds was introduced in Catalonia in 1998. The aim of this study was to investigate the evolution of hepatitis A outbreaks in Catalonia and estimate the preventable fraction of cases associated with outbreaks as a measure of the impact of the vaccination program. Hepatitis A outbreaks reported to the Health Department between 1991 and 2012 were analyzed. The incidence rates of outbreaks, outbreak-associated cases and hospitalizations were calculated. The preventable fraction (PF) and 95% confidence intervals (CI) were estimated for the whole study period (pre-vaccination and post-vaccination) and the post-vaccination period. One-hundred-eight (108) outbreaks (rate of 2.21 per 106 persons-year) were reported in the pre-vaccination period and 258 outbreaks (rate of 2.82 per 106 persons-year) in the post-vaccination period. The rate of cases associated with outbreaks was 1.52 per 105 persons-year in the pre-vaccination period and 1.28 per 105 persons-year in the post-vaccination period. Hospitalization rates were 0.08 and 0.75 per 106 persons-year, respectively. The number of person-to-person outbreaks whose index case was a school contact decreased in the post-vaccination period (aOR 2.72; 95%CI 1.35-5.48), but outbreaks whose index case was a man who has sex with men (MSM) or an immigrant increased. The PF of all out-break-associated cases was 6.46% (95%CI 3.11-9.82) and the highest PF was in the 15-24 years age group (42.53%; 95%CI 29.30-55.75). In the 0-4 years age group, the PF was 18.35% (95%CI 9.59-27.11), suggesting a protective herd effect in unvaccinated subjects. Vaccination of immigrants traveling to endemic countries and MSM should be reinforced.

Original languageEnglish (US)
Pages (from-to)192-197
Number of pages6
JournalHuman Vaccines and Immunotherapeutics
Volume11
Issue number1
DOIs
StatePublished - Jan 1 2015

Keywords

  • Hepatitis A
  • Hospitalization
  • Incidence rate
  • Mass immunization program
  • Outbreak
  • Preventable fraction

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Pharmacology

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