Explore your options: Modified-live and killed vaccines   

(Journal photo by Jennifer Theurer.)

A sound vaccination protocol lays the groundwork for a healthy herd. Taking time to understand the different vaccine options is an important part of making informed decisions that ensure your cattle are in the best position possible to navigate disease challenges.  

“Both modified-live virus and killed virus vaccines have been shown to protect cattle against common respiratory and reproductive diseases; however, there are some key differences in how each of them stimulates immunity,” said Dr. Craig Jones, DVM, director of cattle professional services veterinarians, Boehringer Ingelheim. “It is important for producers to understand the advantages and limitations associated with each.” 

Modified-live virus vaccines

MLV vaccines contain a weakened, or attenuated, form of a live virus. Because the virus has been altered, it should not cause clinical disease, but will very closely mimic a true infection.  

Once the vaccine is administered, the virus will replicate within the animal’s system and create the opportunity for an immune response. Compared to KV vaccines, MLV vaccines generally provide a more rapid, longer-lasting and broader immunity with one dose, since the virus is able to replicate and behave closer to the way it would during a natural infection.¹ 

Although MLV vaccines may stimulate a broader, more complete immune response, there are some other factors to consider. “Modified-live virus vaccines have a greater risk of causing an abortion in pregnant cows, if not used appropriately and according to label,” explained Jones. “In addition, MLVs must be reconstituted [mixed], and may require more attention to detail when it comes to proper use, handling and storage. These factors do not preclude my use or recommendation of MLVs; they are simply things we must keep in mind prior to and when using.”  

Once MLVs are mixed, they should be kept cold and out of sunlight. Following Beef Quality Assurance guidelines, mix only as much vaccine as can be used in one hour or less. MLV products should not be stored for later use.  

Killed virus vaccines

KV vaccines are safe at all stages of pregnancy. They typically do not require reconstitution, and they have a longer shelf life relative to MLV vaccines.   

The immune response following use of a KV vaccine will be slower to develop. “Killed vaccines contain an inactivated, or killed, antigen that is incapable of replicating in the animal’s system,” Jones pointed out. Because the killed virus does not replicate, it usually requires a booster dose in two to four weeks to stimulate a complete immune response. 

“As compared to MLV vaccines, a dose of killed virus vaccine may contain more viral antigen, or pieces of the virus, in order for the immune system to recognize and respond to the antigen,” confirmed Jones. “Because there is more antigen needed, killed vaccines often cost more.” 

Things to consider

“When it comes to building a protocol, you don’t necessarily have to choose between the two types of vaccines,” advised Jones. “In fact, there are many veterinarians and producers who choose to incorporate both options into their protocols.”  

Below are some things to consider when choosing the products to best protect against the disease challenges facing your cattle:  

1. Work with a veterinarian.

“The whole point of vaccination is to help animals remain healthy, while minimizing the risk of economically important diseases that are prevalent in the area where the cattle are being, or will be, managed,” Jones stressed.  

Your local veterinarian can help guide this discussion and provide insight as to which diseases are economically significant and prevalent. Whether you’re talking about parasite management or protecting against reproductive and respiratory losses, working with a veterinarian is the first step.  

2. Have a written herd health calendar. 

Once you have determined which diseases you should vaccinate against, consider using a herd health calendar to help with timing. This will ensure that vaccines are given prior to any potential health risks and your cattle are protected.  

“I always recommend having a written health protocol and records of vaccine and other product administration,” said Dr. Jones. “When health activities are recorded and visible for others in the operation to see, we have greater protocol compliance and more awareness of herd health events.” 

3. Stay on label. 

Different types of vaccines behave differently and will perform differently. Paying attention to the label is extremely important, and will ensure the vaccine is aligned with your expectations. Product labels will also inform you about the correct route of administration and the dose needed. 

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