Hepatitis A seroprevalence in a random sample of the Turkish population by simultaneous EPI cluster and comparison with surveys in Turkey.

This study was conducted to determine the hepatitis A virus (HAV) seroprevalence in nine provinces representative of Turkey as a whole. These provinces are representative of the country's geographical location, and demographic, economic and social characteristics. In each province, sample sizes were determined using published data on HAV seroprevalence, and sample sizes for each province and for the cluster were calculated for each group of subjects under the age of 30 for seroprevalence estimates within a 95% confidence interval. The samples were selected by a cluster method, and the planned recruitment was a total of 4,800 subjects, including 600 subjects each from five large provinces (Istanbul, Ankara, Izmir, Adana, Diyarbakir) and 450 subjects from each of the remaining four provinces (Samsun, Erzurum, Trabzon, Edirne). These numbers were distributed in accordance with the percentages for age groups in five-year increments starting from age five for the population under the age of 30 living in the rural and urban areas in each province. This study of 4,462 subjects under the age of 30 in nine provinces of Turkey identified an overall HAV seroprevalence rate of 71.3%. The distribution of HAV seroprevalences by age showed a steady increase from one year of age from 42.7% to 91.1% at 25-29 years of age. HAV seroprevalence was slightly higher in female subjects (73%) than in male subjects (69.3%). By educational status, seroprevalences were comparable except in young children under age six. Seroprevalence was notably higher in large families with six and more members (80.1%) than in small families with five or fewer members (66.7%). According to our study results, 50% of Turkish children are seropositive for HAV by the age of 10 years. We believe the date support the need for a routine primary immunization policy in Turkey and the development of effective prophylactic programs after possible exposure. Consequently, an immunization policy can be developed for each region according to its epidemiological conditions.