Dr. Jim Roth, IowaStateUniversity, has found that calves with maternal antibody between 1 and 7 weeks of age will not make antibody in response to vaccination with a modified-live virus (MLV) BVDV vaccine. “However, even the youngest calves had a T-cell response to the vaccine and were protected from a virulent type 2 BVDV challenge,” he says. “Therefore, you can't rely on antibody to tell you if the calf is protected by vaccination.” The calves did not develop either antibody or T cell responses to BHV1, BRSV or PI3 when vaccinated in the face of maternal antibody. “The data suggests that maternal antibody blocks both humoral and cell-mediated immunity to those virus vaccines in young calves.” The bottom line, Roth says, is that you can use MLV BVDV vaccines in young calves with maternal antibody and expect good protection from disease.