Your Herd Vaccinations May not Always be Successful? Why?
We hear a lot about how to protect yourself and others right now… and it is especially important to me because I am in a high-risk group (over 65 with underlining health conditions). In the Dairy Industry, we deal with high-risk groups every day–cows that have just calved and newborn calves less than 75 days of age.
Herd immunity threshold (percent of animals that are immune) varies by the disease, but it usually means that 80 to 95 percent of the herd has antibody immunity to the virus or bacteria. How do dairy animals get antibody immunity? They become infected and survive the disease or we vaccinate them for the disease. The problem? Vaccination is not always successful. There are many reasons why a vaccine may not be successful, and many are within your control, but here are a handful of the reasons:
- The animals may not be healthy enough to respond to the vaccine. Think of giving a vaccine to a sick animal or a fresh one. Sometimes we do not even know because it is during the incubation stage before any clinical signs.
- The timing between the vaccine and when the disease breaks is too soon. I coauthor a presentation at American Association of Bovine Practitioners on vaccines that work in the field. There are very few vaccines that have worked successfully in the field. The qualification to be approved by the USDA is only to show that it elicits an antibody response.
- The vaccine was mishandled.Any of the following reasons will reduce potency:
- Not storing at 2°–8°C. (36 to 46 F) Prolonged exposure to higher temperatures and/or direct sunlight may adversely affect potency. Do not freeze.
- Not using the entire contents when first opened.
- Not using sterilized syringes. Do not sterilize with chemicals because traces of disinfectant may inactivate the vaccine.
- Injected incorrectly by putting intramuscular vaccine subcutaneously.
- The vaccine never makes it into the animal
- The virus or bacteria is a different strain than the vaccine. For example, most IBR vaccines protect 2 strains of the virus and there is no cross-protection for the other strains. One herd that I work with closely has IBR Type 4 abortions. There are no commercially available vaccines that cover type 4.
- Most vaccines require a loading dose and a follow up (some require two follow up vaccines). The spacing between these injections is important as well as the follow up itself to get the long term immunity.
- In young calves some vaccines are blocked by the maternal antibodies. These come from colostrum and can be blocked for up to 4 months.
- Not giving the vaccine often enough. For example, the duration of immunity for the IBR vaccine is only 6 months. There is also a difference in the longevity of immune response from modified live vaccines and killed vaccines.
- Giving too many vaccines at once. I have seen a lot of dairy calves worked through a chute at dehorning that received the following: IBR, BVD, BRSV, Lepto 5, 8-Way Clostridia, and Bangs. That is 17 different vaccines that the animal is supposed to respond too. On top of that, the dehorning and work through the chute is traumatic and can cause corticoid steroid release that will also suppress responsiveness.
- The use of too many gram-negative vaccines at the same time. Gram Negative vaccines suppress the immune response.
As you can see there is a lot to think about. I would encourage a great discussion with your veterinarian to plan out how to improve your Herd Immunity.