Administering a well-planned vaccine program is the most cost-effective health investment a dairy producer can make, according to Mark van der List, BVSC, MPVM, senior professional services veterinarian for Boehringer Ingelheim Vetmedica, Inc., based in Davis, Calif.
Yet establishing vaccine protocols is a herd-by-herd scenario, he advises. “Successful vaccination -- which implies immunity from disease-- depends on the herd’s specific disease challenges, geography and management systems,” says vander List.
There are differences in the types of vaccines that may be selected to manage a herd’s disease-prevention program. Most vaccines fall into the category of either “killed” or “modified live (MLV).”
In killed or inactivated vaccines, the pathogen for the target disease is contained in the vaccine but is no longer living. Modified live vaccines, on the other hand, contain living organisms that have been altered to reduce the virulence of the disease-causing pathogen. While still alive, these organisms have been rendered non-virulent by specific vaccine manufacturing techniques. “A return to virulence in MLVs is possible but extremely rare,” says vander List.
MLVs require the non-virulent pathogens to replicate in the animal, whereas killed vaccines do not. Therefore, care must be taken when handling MLVs to protect the living organisms so the vaccines remain effective.
To obtain an appropriate immune response from killed vaccines, these productsusually containadjuvants, which are additional compounds included in the vaccine. Examples of adjuvants include oil, saponins and aluminum hydroxide. These substances help stimulate the immune system to recognize the killed organism in the vaccine. To obtain an adequate immune response from a killed vaccine,vander List says initially two shots of the same killed vaccine, spaced three to eight weeks apart, are required. Yearly boosters then are recommended
The veterinarian says the advantages of killed vaccines include:
- Extreme safety, with no risk of an organism reverting to virulence and infecting the vaccinated animal or its herdmates. Killed vaccines also are safe for pregnant and immunocompromised animals.
- Longer storage life and greater tolerance of field conditions than MLV vaccines. MLVs, conversely, must be administered within one to two hours of reconstitution and may be damaged by heat, sunlight and cold.
MLVs, on the other hand, offer the following advantages:
- A stronger,cell-mediated immune response, plus the initial vaccination usuallyrequires only one dose to infer immunity. However, because a small percentage of animals may not respond to a vaccine on a given day, it is recommended to repeat the vaccine at a later date.
- Lower incidence of injection-site lesions, which sometimes can be caused by the adjuvants in killed vaccines.