Clinical and laboratory features of viral hepatitis A in children

Effectiveness of hepatitis A vaccination as post-exposure prophylaxis

Hepatitis A (HA) has been a vaccine-preventable disease since 1995. In Catalonia, a universal combined hepatitis A+B vaccination program of preadolescents was initiated at the end of 1998. However, outbreaks are reported each year and post-exposure prophylaxis (PEP) with hepatitis A virus (HAV) vaccine or immunoglobulin (IG) is recommended to avoid cases. The aim of this study was to assess the effectiveness of HAV vaccine and IG in preventing hepatitis A cases in susceptible exposed people. A retrospective cohort study of contacts of HA cases involved in outbreaks reported in Catalonia between January 2006 and December 2012 was made. The rate ratios and 95% confidence intervals (CI) of HA in susceptible contacts receiving HAV or IG versus those without PEP were calculated. There were 3550 exposed persons in the outbreaks studied: 2381 received one dose of HAV vaccine (Hepatitis A or hepatitis A+B), 190 received IG, and 611 received no PEP. 368 exposed subjects received one dose of HAV vaccine and IG simultaneously and were excluded from the study. The effectiveness of PEP was 97.6% (95% CI 96.2-98.6) for HAV vaccine and 98.3% (95% CI 91.3-99.9) for IG; the differences were not statistically significant (p = 0.36). The elevated effectiveness of HAV vaccination for PEP in HA outbreaks, similar to that of IG, and the long-term protection of active immunization, supports the preferential use of vaccination to avoid secondary cases.

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

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.