Vaccines should be viewed as tools in our armamentarium for the prevention of BRDC, and it should be realized that they have limitations. Vaccination programs for the feedlot should be developed between the producer and veterinarian and in consideration of farm goals, expected outcomes, and cost benefit. This response is optimal only in a normal, reasonably healthy animal. An animal responding satisfactorily is said to be immunized. Vaccination does not equal immunization.
Time is needed for an adequate response to vaccines.
Significant antibody levels may not be reached for 14 to 21 days in many cases and may only be reached following a booster dose in others. Multiple strains of some viruses and bacteria exist in the field. Vaccines may not always be available which protect against all strains. Live and killed vaccines are both available and each has distinct advantages and disadvantages. MLV vaccines are generally cheaper than killed virus vaccines but require a normal immune system to work.