A comparative study of the seroprevalence of the population of the Odesa region in relation to the hepatitis A (HA) virus was carried out, which was investigated in the years of different intensity of the epidemic process of hepatitis A. In 2004, when the incidence of HA among the pediatric population of the region was 96.14, among adults — 12.91, general population — 37.10 per 100 thousand population, the seroprevalence of children under 10 years was 68.25%, children population up to 15 years — 71.95%, persons under 30 years — 77.97%, over 30 years — 97.14%.
In 2015, at the incidence rates of children under 17 years old — 1.8, adults — 1.31, of the general population — 1.38 per 100 thousand, the seroprevalence of children under 10 years was 22.26%, under 15 years old — 20.31%, persons under 30 years old — 33.33%, over 30 years — 86.25%. According to the results of the study of seroprevalence, according to the resolution of the WHO, the Odessa region of Ukraine in the present period can be attributed to the territories with low endemicity of the epidemic process of HA, whereas in 2004 it was the territory with the average level of endemicity. The findings indicate that there is a possibility to solve the problem of immunization of children and and adults with liver disease at the local level.