Public Health

Children key to hepatitis A control in urban areas of developing countries

Last Updated: 2006-02-10 13:46:50 -0400 (Reuters Health)

By Megan Rauscher

NEW YORK (Reuters Health) - Children, especially young children, are good candidates for hepatitis A vaccine in urban areas of developing countries struggling with an increasing hepatitis A disease burden, according to the results of a study conducted in one such area: Almaty, Kazakhstan.

"This study shows that in a place with very strong seasonal hepatitis A outbreaks that look like community outbreaks that might be food or water-borne, there actually is a very large amount of person-to-person transmission occurring in the background as well," Dr. John C. Victor told Reuters Health.

Almaty has a population of 1.14 million, making it the largest city in Kazakhstan. While the reported annual incidence of hepatitis A varies widely in this city, epidemics occur each year between September and March and clusters of cases are often identified in households, daycare centers and schools.

Over a recent 16-month period, Dr. Victor, from the University of Michigan in Ann Arbor, and colleagues at the US Centers for Disease Control and Prevention and the Kazakhstan Ministry of Health, investigated hepatitis A transmission patterns in Almaty by studying household and daycare/school contacts of people with hepatitis A infection.

They identified 756 hepatitis A cases for an annualized incidence of 161 cases per 100,000 persons. Most of these cases occurred among young children, they observed.

Household contacts of case subjects had 35 times the odds of becoming infected as did daycare and school contacts. Within households, younger age of either the infected person or susceptible contact increased the odds of transmission.

The investigators note, in the February 1st American Journal of Epidemiology, that by the time symptomatic index cases were identified, "half of transmission had already occurred, having been detected retrospectively."

These findings, write the authors, "broaden and strengthen our view that unrecognized person-to-person transmission among young children plays a primary role in sustaining hepatitis A epidemics, even in developing areas of intermediate endemicity."

Targeted hepatitis A vaccination of children may prove effective and sustainable in developing countries, the authors conclude.

"We known that vaccinating children in the US has been extremely effective in bringing down the overall incidence of hepatitis A and likely targeting children in other countries will probably be effective as well," Dr. Victor told Reuters Health.

He and his colleagues already have evidence to support this. In the 3 years since their transmission study, Dr. Victor's group been conducting a vaccine study among young children in Almaty with "promising results," he said.

Am J Epidemiol 2006;163:204-210.