Immunization program in Israel resulted in 95 % reduction in hepatitis A incidence
Jul 13, 2005 - 12:14:38 PM
A national immunization program for infants in Israel has resulted in a 95 percent reduction in overall hepatitis A incidence, according to a study in the July 13 issue of JAMA.
Until 1999, Israel was considered a country with intermediate hepatitis A virus endemicity (a disease constantly present to greater extent in a particular locality). Although the overall incidence has been progressively decreasing since the 1960s, the annual reported incidence during the 1992-1998 period ranged from 33 to 70 per 100,000 population, with marked fluctuations. Reports of outbreaks, especially those involving young children, increased. Because most young children have asymptomatic or unrecognized infection, they play an important role in hepatitis A virus transmission as a source of infection. Therefore, routine childhood vaccination would theoretically prevent infection in age groups that account for a substantial proportion of cases, eliminate a major source of infection for other children and adults, and eventually prevent infections in older persons as vaccinated children grow to adulthood, because immunity to hepatitis A virus by vaccination is long-lasting.
Health officials in Israel decided to introduce universal vaccination of toddlers against hepatitis A because of epidemiologic evidence and a cost-benefit analysis of the program. The program started in July 1999 and is included in the National Health Services list so that the vaccine is given free of charge. A dose is given at ages 18 and 24 months. Immunization of older high-risk groups, such as drug users, continued.
Ron Dagan, M.D., of Ben-Gurion University of the Negev, Beer-Sheva, Israel, and colleagues examined the impact of the toddlers-only vaccination program of hepatitis A disease in all ages in the 5.5 years following initiation of the program. Overall vaccine coverage in Israel in 2001-2002 was 90 percent for the first dose and 85 percent for the second dose.
A decline in disease rates was observed before 1999 among the Jewish but not the non-Jewish population. The researchers found that after initiation of the program, a sharp decrease in disease rates was observed in both populations. The annual hepatitis A incidence rate of 2.2 to 2.5 per 100,000 during 2002-2004 represents a 95 percent or greater reduction for each year with respect to the average incidence during 1993-1998 (50.4 per 100,000). For children aged 1 through 4 years, a 98.2 percent reduction in hepatitis A disease was observed in 2002-2004, compared with the prevaccination period. However, a sharp decline was also observed in all other age groups (84.3 percent [less than 1 year], 96.5 percent [5-9 years], 95.2 percent [10-14 years], 91.3 percent [15-44 years], 90.6 percent [45-64 years], and 77.3 percent [65 years or older]). Among the Jewish population in the Jerusalem district, in whom the active surveillance program was successfully conducted, a more than 90 percent reduction of disease was demonstrated. Of the 433 cases reported nationwide in 2002-2004 in whom vaccination status could be ascertained, 424 (97.9 percent) received no vaccine and none received 2 doses.
"In the next decade, many regions worldwide will move from a state of high endemicity to a state of intermediate endemicity. The Israeli program of universal toddlers-only vaccination can serve as a paradigm of a simplified model of effective vaccination for both developed and developing countries," the authors conclude.
In an accompanying editorial, Pierre Van Damme, M.D., Ph.D., and Koen Van Herck, M.D., of the University of Antwerp, Belgium, comment on the studies in this week's JAMA on hepatitis A vaccination programs.
"The baseline differences in disease incidence between vaccinating and nonvaccinating states in the United States on which the universal vaccination recommendations were determined were eliminated and the incidence gap between high and intermediate endemic populations in Israel was narrowed or almost closed. Vaccination was a major contributor to these declines but, as discussed by both sets of authors, it is difficult to evaluate to what extent the observed reduction of the hepatitis A virus incidence rate could be attributed to improved environmental and hygienic conditions or to the epidemic cycles that characterized the epidemiology of hepatitis A virus in the past. Only continued disease surveillance will allow confirmation of the real impact and added value of these mass vaccination programs."
"...if administration of multiple vaccines or combination vaccines is not an issue, and if the vaccine cost is reasonable, toddlers-only or childhood immunization programs could become a realistic strategy in countries and regions where endemicity is shifting from high to intermediate, a situation that will increase in the next decade worldwide," the authors conclude.
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