title: Changes in the epidemiology of hepatitis A outbreaks 13 years after the introduction of a mass vaccination program.
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 10(6) persons-year) were reported in the pre-vaccination period and 258 outbreaks (rate of 2.82 per 10(6) persons-year) in the post-vaccination period. The rate of cases associated with outbreaks was 1.52 per 10(5) persons-year in the pre-vaccination period and 1.28 per 10(5) persons-year in the post-vaccination period. Hospitalization rates were 0.08 and 0.75 per 10(6) 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 outbreak-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.
authors.affiliation: a Public Health Agency of Catalonia; Generalitat of Catalonia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Martínez
authors.forename: Sonia
authors.initials: S
authors.lastname: Broner
authors.forename: M Rosa
authors.initials: MR
authors.lastname: Sala
authors.forename: Sandra
authors.initials: S
authors.lastname: Manzanares-Laya
authors.forename: Pere
authors.initials: P
authors.lastname: Godoy
authors.forename: Caritat
authors.initials: C
authors.lastname: Planas
authors.forename: Sofia
authors.initials: S
authors.lastname: Minguell
authors.forename: Nuria
authors.initials: N
authors.lastname: Torner
authors.forename: Mireia
authors.initials: M
authors.lastname: Jané
authors.forename: Angela
authors.initials: A
authors.lastname: Domínguez
authors.forename: The Working Group
authors.initials: TW
authors.lastname: For The Study Of The Immune Status In Health Care
authors.forename: For The Study Of
authors.initials: FT
authors.lastname: Hepatitis A In Catalonia
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006506:Hepatitis A / Q000453:epidemiology* / Q000517:prevention & control*; D022362:Hepatitis A Vaccines / Q000008:administration & dosage*; D017325:Hepatitis B Vaccines / Q000008:administration & dosage; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D032541:Mass Vaccination / Q000379:methods*; D008875:Middle Aged; D012307:Risk Factors; D012725:Sexual Behavior; D013030:Spain / Q000453:epidemiology; D055815:Young Adult
chemical_list: D022362:Hepatitis A Vaccines; D017325:Hepatitis B Vaccines
keywords: Hepatitis A; hospitalization; incidence rate; mass immunization program; outbreak; preventable fraction