WASHINGTON — Vaccinating all toddlers against hepatitis A reduced the overall viral incidence by 95% in one Israeli community, Dr. Beth P. Bell said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
In an investigation led by Dr. Ron Dagan of the Soroka University Medical Center, Be'er Sheva, Israel, the community began vaccinating children aged 18–24 months in 1999. By 2002–2004, the annual incidence of hepatitis A was 2.2–2.5 cases per 100,000 people, which represents a 95% decline in viral incidence relative to prevaccinated levels (JAMA 2005;294:202–10).
This outcome is the result of herd immunity, said Dr. Bell of the Centers for Disease Control and Prevention's Division of Viral Hepatitis in Atlanta.
“What we've learned about what happens in communities when you use hepatitis A vaccine among children is that there's evidence of considerable cohort effects both among unvaccinated children and also among adults. Early results indicate impressive overall public health impact with quite modest vaccination coverage,” said Dr. Bell, who presented the results on behalf of Dr. Dagan.
The 1− to 4-year-old age group, the population at the highest risk of contracting hepatitis A, saw the greatest decline in incidence, with a 98.2% drop, compared with the prevaccinated period.
In addition, the findings indicate that hepatitis A disparities that existed between the Jewish and non-Jewish populations have been almost completely eliminated after the universal vaccination protocol was introduced.