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MLV and Killed Vaccines Both Have a Home on the Dairy

Mar 10, 2013

Understanding the differences between killed and modified-live vaccines can provide better protection from disease.

Brian Miller Photo   2Dr. Brian Miller, Professional Services Veterinarian, Boehringer Ingelheim Vetmedica, Inc.

Vaccination plays an integral role in keeping dairy herds healthy and productive, but despite having such a fundamental role, the function of the vaccines we choose is quite complex.

Understanding the differences between modified-live virus (MLV) vaccines and killed vaccines allows veterinarians and producers to use them properly and at appropriate times.

Let’s look at the definitions of these two categories. A modified-live vaccine contains a small quantity of bacteria or virus that has been altered, so that it is no longer capable of causing clinical disease, but is still capable of mimicking natural infection by replicating within the animal, creating an immune response and subsequent immunity. A killed vaccine, however, has been altered so the virus or bacteria is dead and cannot replicate. Typically, killed vaccines contain large amounts of antigen and utilize adjuvant(s) to enhance the immune response.

Both modified-live and killed vaccines have a place on the dairy, and their function can be summed up in two words: robustness combined with safety when used on label, and safety respectively. A simplified description, perhaps, but these two words carry heavy meaning for vaccines.

For example, a modified-live vaccine generally provides a more robust, long-lasting response, because the animal "sees" all the different stages of the replicating (multiplying) virus or bacteria. Modified-live vaccines like Express® FP 10 are commonly used in a dairy herd because they provide greater and longer-lasting immunity.

A common concern when using modified-live vaccines is safety. EXPRESS FP 10, when used according to label directions, is safe to use in pregnant cows provided they were vaccinated, according to label directions, with any EXPRESS FP vaccine within the past 12 months. If you choose not to use a modified-live vaccine during pregnancy, a killed vaccine is an alternative choice. Consult with your veterinarian regarding this decision.

With killed vaccines like Triangle®, we typically think of safety. Modified-live vaccines should not be used in pregnant animals with an unknown vaccination history. When dealing with this type of situation, killed vaccine products are a safer choice.

Disadvantages of killed versus modified-live vaccines include a slower onset of immunity, shorter duration of immunity, the need for multiple doses to stimulate initial immunity, and unresolved issues regarding the robustness of the immune response following their use.

There are regional differences when it comes to vaccine usage but many dairies use a core vaccine protocol that includes a 10-way (five-way viral and five-way Lepto) and a seven- or eight-way clostridial. While these two vaccines often serve as the foundation of a vaccine protocol, additional vaccines used might include protection against respiratory bacteria, Salmonella or pink eye.

To develop the most effective vaccine protocol utilizing both modified-live and killed vaccine products, work closely with your herd veterinarian. Take compliance seriously, and remember to always follow label directions to optimize immunity in each animal, and provide greater overall immunity and protection for your dairy herd.

Regardless of MLV or killed vaccination preferences, Boehringer Ingelheim Vetmedica, Inc has the broad vaccine portfolio with proven protection to satisfy the needs that are most important to you and the success of your herd.

For more information, visit

Express and Triangle are registered trademarks of Boehringer Ingelheim Vetmedica, Inc. ©2013 Boehringer Ingelheim Vetmedica, Inc.

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