Abstract: The study was designed to evaluate neutralizing (SN) antibodies against bovine viral diarrhea virus (BVDV) in the calves vaccinated with the live attenuated bovine viral diarrhea virus SM vaccine. A total of 30 healthy calves at weaning were randomly divided into two groups, with 15 calves in vaccinate group and 15 in control group. The attenuated BVDV SM vaccine strain was administrated via intramuscular injection on the neck at a single dose and challenged with a virulent BVDV-JL virus by nasal spray. The blood samples were collected at different time points for monitoring SN antibody titers. The results indicated that the SN antibody titers in the vaccinated calves maintained at a relative high level until 12 month post-vaccination, and the vaccinated calves were effectively protected from the challenge, as detected by the white blood cell count (WBC) and virus shedding. Therefore, the duration of immunity of the vaccine was at lease for 9 months.

Key words: bovine viral diarrhea virus (BVDV); live attenuated vaccine; duration of immunity; protectio effect