Calfhood infection is usually transient. However, there is evidence that some calfhood infections go through a latent period and reactivate following puberty. Vaccination is a helpful tool in maintaining resistance to brucellosis in a cattle population. Two-thirds of cattle properly vaccinated will resist moderate exposure. No animal can be considered immune to severe exposure.
Vaccination is required for breeding females to be moved into some states.
The acceptable age for brucellosis vaccination is 4 to 10 months. Only heifers should be vaccinated. The veterinarian is required to put a designated tattoo in the right ear and record the vaccination with the state veterinarian. Vaccinated dairy heifers are excused from testing until 20 months of age or until heavy with calf. It is spread from cow to cow only by a bull in natural service.