Whenever I see a vaccine fail to produce the benefits expected, I am presented with a teachable moment. In addition to explaining why vaccines can sometimes fail, I also take the opportunity to explain how producers can help tip the scales in their favor when it comes to vaccine success.
Understanding immune systems
Animals have two types of immunity. “Non-specific” immunity protects the animal against many types of invading organisms. Examples include microscopic cilia, or hairs, which line the lungs and trap bacteria and particles in the air, and then force them back out of the airways. Or, white blood cells circulating in the bloodstream that engulf and destroy invading bacteria.
Animals also have “specific” immunity that protects them against a single organism. Vaccines work primarily to stimulate specific immunity, which, in turn, helps the animal mount a defense to keep the infectious organisms below a threshold level or tipping point where disease can occur.
The goal of vaccination is to create a “memory” and an environment where invading organisms are killed faster than they can multiply. However, vaccines are only one part of the equation. For vaccines to work properly, you also must manage the animal’s environment and make sure that the scales don’t tip in favor of the invading organism. Here are three areas where producers can make the biggest impact:
1. Prevent overwhelming challenge.
No matter how efficient the immune system’s memory and response, disease may occur if a large number of invading organisms are present. Despite vaccination, pneumonia can occur if ventilation is poor, and E. coli calf scours can occur if the milk fed to calves has high levels of bacteria due to poor sanitation or storage. Attention to hygiene and a proper physical environment are key to a successful disease-prevention program.
2. Help the non-specific immune system to function well.
Several conditions, such as environmental stress or malnutrition, can suppress the immune system. Research has shown that periparturient cows, in general, suffer from some degree of immunosuppression. And specific triggers, such as mycotoxin-contaminated feed or stray voltage on a farm, can suppress immune function. Even if the vaccination has induced appropriate memory, the vaccine may appear to fail under certain immunosuppressant conditions. Providing a proper diet and a clean environment will help, along with timing vaccines so that they do not occur on top of stressful events such as weaning or calving.
3. Follow vaccine protocols.
Inadequate stimulation of vaccine-induced “memory” can occur if you fail to follow label directions. Most killed vaccines require at least two doses given within two to six weeks of each other to effectively stimulate memory and immunity. Most modified-live vaccines only require one dose, but it takes several weeks before effective memory is induced. If infection occurs before this sequence of events has occurred, the immune system will not be able to wage a proper battle against an infection. Or if vaccination occurs under certain immunosuppressant conditions, memory will not be adequate to fight off a future disease challenge.
Vaccination is a tool. It helps tip the balance in favor of the animal’s natural immune defenses. Work with your veterinarian to address any issues that you might have to work on. It will set up an opportunity for your vaccination program to succeed and deliver the intended results.
Brian Gerloff is a veterinarian and operates Seneca Bovine Service in Marengo, Ill.