Background & Objectives: Regarding the admitted cases at early infancy in Tabriz Pediatrics Medical Center, this research was carried out to determine the role of Hep.B. vaccination in the incidence of ITP.

 Methods: We studied all patients’ admission files in Tabriz Pediatrics Center from 1993 to 2002. The patients were under 6 months of age and hospitalized with the impression of ITP. There were 25 infants whose ITP was diagnosed upon their clinical findings, blood counts and bone marrow aspiration and confirmed by exclusion of other causes of thrombocytopenia. Hep. B. vaccination has been included in routine immunization in Iran since 1993. In order to compare the incidence rate of ITP before and after 1993, we also sought all ITP patients’ files at the same age group who had been admitted to Tabriz Pediatrics Center during the decade before the beginning of routine Hep.B. vaccination (i.e. 1982 to 1992).

 Results: This study shows a considerable increase in incidence of ITP in infants under 6 months of age between 1993 asnd 2002 compared to the decade before the beginning of Hep.B.vaccination, which is statistically significant (P=0.0029).

 Conclusion: Although there is no facility to measure antibodies in Iran and many other countries, and this is one of the reasons for lack of proof for existence of a relationship between vaccination and ITP incidence, the study of cases in two different periods may strengthen the role of Hep.B. vaccination in the occurrence of ITP at early infancy.