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