Experts have long believed that universal hepatitis A vaccination for children is an effective strategy to reduce disease incidence. This study coincides with the recent unanimous decision of the Advisory Committee on Immunization Practices (ACIP), an advisory body to the Centers for Disease Control and Prevention (CDC), recommending universal hepatitis A vaccination for all children between 1 and 2 years of age. The ACIP recommendation marks a milestone in the fight against the disease in the
Titled "Universal Toddler Hepatitis A Virus Vaccination: An Opportunity for the Elimination of Population Disparity in Disease Incidence," the study by Dagan highlights the fact that before vaccination, one-fifth of all toddlers in a hepatitis A endemic community had high hepatitis A antibody levels indicating previous exposure. This was reduced by 90 percent within three years after initiation of the toddler-only universal vaccination program. In addition, a distinct disparity in hepatitis disease incidence between the Jewish and non-Jewish population, related to differences in social and economic living conditions, was practically eliminated, due to a very impressive reduction in disease in both populations following vaccination.
"This study demonstrates the significant impact the hepatitis A vaccine can have on the overall population," said Dagan. "Vaccinating all toddlers not only resulted in a dramatic reduction of hepatitis A incidence in an age group in Israel vulnerable to the disease, but also offers objective proof of the rapid vaccination-induced reduction of hepatitis A circulation, and the positive effect vaccination can have, on that community."
The study presented by Dagan follows the fluctuation in hepatitis A incidence rates among the Israeli population. Since 1999, coinciding with the introduction of the hepatitis A vaccine to all toddlers at 18 and 24 months, overall levels of hepatitis A incidence have been reduced by 95 percent, supporting the belief that the immunization of toddlers in the 18 to 24 month bracket confers "herd immunity," the protection extended to family members and the community in general when a large portion of a population is vaccinated.
In addition, the most significant decrease in hepatitis A levels after the introduction of hepatitis A immunization in toddlers was seen in the 1- to 4-year age bracket -- a demographic that is historically the most susceptible to this type of infection. There was almost 100 percent (98.5 percent) decrease in reported incidences among this demographic.
These findings are consistent with the recent study by Wasley et al ("Incidence of Hepatitis A in the United States in the Era of Vaccination," Journal of American Medical Association, July 13, 2005) which shows sustaining and further reducing hepatitis A incidences in the United States can be achieved by improving vaccination coverage in groups for which it is currently recommended. Similar to the Israeli study, Wasley et al found that a decline in hepatitis A infection rates in children occurred with the mandated vaccination of one age group and helped reduce transmission in other age groups, supporting the hypothesis of a strong herd immunity effect. Wasley et al concluded that elimination of hepatitis A would require expansion of current recommendations to include routine vaccination of all children. The unanimous ACIP decision to recommend incorporating hepatitis A vaccination into the children's immunization schedule reinforces the need to improve and enhance the health and well-being of children by helping to protect them from this serious and highly contagious disease.