The aim of this study was to examine the changes in the indicators of free radicals and antioxidant activity, represented by malondialdehyde and glutathione peroxidase in the sera of ewes vaccinated with Rev 1 vaccine. The experiment included 28 animals which were divided into four equal groups. Animals of the first and second groups were vaccinated subcutaneously with 2×109 and 2×107 colony forming units (CFU), respectively, whereas the animals of third and fourth groups were vaccinated conjunctively with 2×109 and 2×107 CFU, respectively. Sera were collected monthly for 6 months. Antibody responses were assessed by classical tests (Rose Bengal test, tube agglutination and 2-mercaptoethanol tests) in comparison with competitive ELISA. The antibody titers were higher and remained for along period in the subcutaneously vaccinated groups with the two doses compared those vaccinated conjunctively. There was a significant increase in serum glutathione peroxidase activity in the 8th week post vaccination in subcutaneously vaccinated groups and during the 12th week in those vaccinated conjunctively. Significant increase of serum malondialdehyde levels occurred during the 4th week in those vaccinated conjunctively and in 8th week in those vaccinated subcutaneously. This study concluded that the route of administration of the vaccine affects glutathione peroxidase activity and malondialdehyde level, which act as indicators of oxidative stress response, more than the vaccine dose.