Infectious disease control through vaccination is an important component of bovine herd health but it is only a part of the total program. Vaccination reduces the probability of catastrophic losses but should not be expected to prevent all losses. The benefits of vaccination are difficult to evaluate and unlike insurance, vaccination provides no compensation when losses occur. Thus, many livestock owners resent the continuous commitment of resources needed for herd immunity because they see few visible returns on investment. Healthy, well-nourished calves vaccinated prior to breeding for IBR, BVD, and PI3 will have reduced probability of aborting or suffering severe disease due to these viruses. Vaccination in the presence of exposure, disease,or during adjustment to new feed or a new environment is risky and should be approached conservatively.The veterinarian should accept the responsibility to invoke available vaccinations in a manner most suited to each management situation so as to provide the maximum protection to the most animals while taking the least risk.