The first question when developing a vaccination protocol may not be, “Which vaccine should I use?” Instead, Dr. Amelia Woolums, endowed professor at Mississippi State University, suggests starting with a more basic question: What is happening on this operation?
Understanding the production system, cattle populations, disease history and timing of disease risk provides the foundation for deciding what vaccination can contribute. From there, veterinarians can weigh the evidence, risks, timing and practicality of the available options. Here are nine considerations to work through when developing or reviewing a cattle vaccination protocol.
1. Understand the Production System and Goals
Before selecting a vaccine, talk with the producer.
“I really think that what we should do is talk to the producer to understand the production system and goals,” Woolums says.
Take the time to understand what happens on the operation throughout the year. When do cattle arrive and leave? Where do they come from? Where do they go? What cattle populations are present? What are the producer’s disease or production concerns?
That conversation can uncover management practices that may otherwise be missed. An operation may have multiple cattle populations, bring in cattle at different times or move animals between facilities, all of which can change disease exposure and vaccination needs.
2. Identify the Cattle Populations and Their Disease Risks
Different groups of cattle on the same operation may have different vaccination needs.
Woolums encourages veterinarians to consider nursing calves, replacement heifers, bulls, home-raised stockers and purchased stocker cattle separately.
The source and management of cattle also influence disease risk. Purchased or commingled cattle may face greater exposure than home-raised animals that remain within a relatively closed population.
For each population, ask: What diseases are these animals likely to encounter? When are they most likely to be exposed? Which of those diseases can vaccination help prevent?
3. Consider the Operation’s Disease History
Past disease problems can provide important clues when developing a vaccination protocol. A disease that is not currently causing problems may still represent a future risk. Woolums describes disease patterns as capable of waxing and waning as exposure and herd immunity change.
“Maybe it was a problem in the past. It’s not a problem now and maybe they’re thinking, ‘well, that problem’s gone,’ but that problem could come back,” she explains.
Historical records and the producer’s recollection of previous disease events can therefore be useful when assessing current risk.
Also consider what is happening on other operations in your practice. Similar management, environmental or weather conditions can create similar disease risks across multiple herds.
4. Use Diagnostics to Clarify Disease Risks
Diagnostics can help determine what is actually causing disease, particularly during a serious outbreak.
Woolums does not believe producers need to collect microbial diagnostic samples constantly. During significant outbreaks, however, she strongly encourages veterinarians to use necropsy and diagnostic investigation.
“If you don’t necropsy the first dead, please necropsy the second dead,” Woolums says.
Waiting until several animals have died can mean losing opportunities to identify the cause of disease and make changes that could prevent additional losses.
State and regional diagnostic laboratory reports can also help veterinarians identify disease patterns occurring elsewhere that could be relevant to their clients.
5. Think Beyond Vaccination
Vaccination should be considered as part of a larger disease-prevention strategy.
The Hazard Analysis and Critical Control Point, or HACCP, approach is a potential framework for identifying where and when disease hazards occur within a production system. The approach involves mapping the production process, identifying points where hazards are likely to occur, establishing targets for intervention and monitoring whether those targets are being met.
“It sounds daunting,” Woolums acknowledges, but says it may be worthwhile.
The full HACCP process used in a food-processing facility may not be practical on a cattle operation. The broader principle, however, can help veterinarians think systematically about disease prevention.
“We all know that vaccination alone isn’t going to control those diseases,” Woolums says. “We need to do other things along with vaccination.”
6. Weigh the Risks and Benefits of Vaccination
Once disease risks have been identified, veterinarians need to consider whether vaccination provides enough potential benefit to justify its costs and risks.
Woolums compares vaccination in some situations to insurance. A producer may never experience a particular disease, but the consequences of an introduction can be serious enough to make prevention worthwhile.
She also cautions against assuming vaccines are completely without risk.
Vaccination can produce an inflammatory response, while adverse reactions, injection-site reactions and other complications are possible even when a licensed product is used correctly. Cost and labor also need to be considered.
The decision should therefore account for the severity and likelihood of disease, the expected vaccine benefit and the potential downsides of vaccination.
7. Evaluate the Quality of the Evidence
Not all evidence supporting a vaccine provides the same level of confidence.
Woolums describes a progression from laboratory measurements of immune responses to experimental challenge studies, field trials and, at the highest level, systematic reviews or meta-analyses.
“Just because an animal has a measurable antibody or cell mediated immune response doesn’t necessarily mean that it is associated with protection,” Woolums explains.
Experimental challenge studies provide additional information by deliberately exposing vaccinated and control animals to a pathogen. However, these studies occur under controlled conditions that may differ from commercial cattle operations.
Field trials can provide a better indication of how vaccination performs under real-world conditions. Woolums encourages veterinarians to look for well-designed field trials and, when available, systematic reviews or meta-analyses.
Even those studies require careful interpretation. Different vaccines, manufacturers and protocols may be grouped together, making it difficult to determine the effect of a particular product or approach.
8. Match Vaccination Timing to Disease Risk
After determining which vaccines may be appropriate, veterinarians need to decide when they should be administered.
Woolums recommends starting with the product label and then considering the principles of vaccinology when developing the protocol.
“Animals need time to respond to vaccination,” she says.
Animals need time to develop an adaptive immune response following vaccination. Woolums suggests thinking in terms of roughly one to two months for the primary immune response to develop, while boosters can be important for establishing or strengthening protection.
Timing should also be based on when disease is expected to occur. The production calendar is equally important. If cattle will not be accessible when a vaccine or booster needs to be administered, the theoretically ideal protocol may not be practical.
For very young calves, that vaccination has limitations. When disease is occurring during the first month or two of life, passive immunity from colostrum and good hygiene remain important prevention tools because there may not be enough time for vaccination to provide the desired protection.
9. Keep Records and Reassess the Protocol
A vaccination protocol should not be considered permanent.
Veterinarians and producers should keep records of the diseases the vaccination program is intended to prevent and use those records to evaluate whether the protocol is achieving its goals.
“I would love for everybody to do their own clinical trials and figure out what works,” she says.
That does not mean every operation needs to conduct a formal research study. Consistent records can help identify whether disease patterns are changing after a vaccination protocol is implemented.
A reduction in disease should not automatically be attributed to vaccination, since other management or environmental factors may have changed. Conversely, continued disease does not necessarily mean a vaccine has failed if the targeted pathogen was not responsible for the disease.
“Records of cases that are intended to be prevented by vaccination should help estimate whether the vaccination protocol should be modified or discontinued,” Woolums says.
Build the Protocol Around the Operation
A vaccination protocol is ultimately a risk-management plan, not simply a list of products.
Understanding the production system, identifying cattle populations and disease risks, considering disease history and diagnostics, evaluating vaccine evidence and weighing benefits against risks can help create a more targeted approach. Timing those interventions around the biology of the vaccine, expected disease risk and realities of the production calendar makes the plan more practical.
Tracking disease and production outcomes can help determine whether the approach is accomplishing what it was designed to do. The most appropriate strategy may differ from one operation to another, and plans should be reassessed as disease patterns, management practices or available evidence change.
