A vaccine against Infectious Necrotic Hepatitis produced in Elazığ Veterinary Control and Research Instıtute was tested in a group of sheep. Ten sheep that have not been previously vaccinated were inoculated 2 ml vaccine twice at 21 day interval. Blood was collected 10 days, 2, 4, 8, 12 and 15 months following the second vaccination and pooled. Antitoxin level was 8 IU/ml on day ten and decreased to 1 IU/ml 10 months later.At the end of the second year antitoxin level was 20 IU/ml and decreased to 1 IU/ml one year later.

Based on the results of the present study it could be suggested that vaccination against infectious necrotic hepatitis of sheep should be repeated 10 months following first vaccination and then repeated yearly.