Post-Vaccination: What to Expect
Vaccination is a cornerstone of your horse’s health plan. It’s one of the safest and most cost-effective ways to help prevent your horse from contracting many infectious — and potentially life threatening — diseases. While the benefits of vaccination far outweigh the risks, it’s important to have realistic expectations when vaccinating your horse.
What Should I Expect?
The goal of administering a vaccine is to stimulate an immune response to help protect your horse from disease. This response creates a cascade of events within the immune system to ward off disease. As a result, some horses may experience mild and transient side effects shortly after vaccination, including low-grade fever (less than 102°F), decreased appetite, fatigue or lethargy, mild heat or swelling at the injection site, and injection-site tenderness.
These signs usually appear within 24 hours after vaccination and typically resolve within 24 to 48 hours.
Vaccine Associated Adverse Events
There are three general categories of types of vaccine associated adverse events (VAAE): 1. Local injection site reactions. These are the most common and generally include localized swelling of various degrees; heat, pain, and/or tenderness at the injection site. These reactions usually show up within 24 hours after vaccination. 2. Systemic reactions. Systemic reactions may result in fever, lethargy, and lack of appetite. Most vaccine-associated fevers and lethargy resolve in 24 to 48 hours without treatment. 3. Allergic systemic reactions. Allergic systemic reactions are very rare and can include sweating, elevated heart rate, respiratory distress, colic, or the development of hives. Call your veterinarian immediately if you see any of these signs.
Why do some horses have VAAEs, and others do not? This is an elusive question that has endured the test of time.
Just as some people have allergies to antibiotics, certain medications, or peanuts, vaccine reactions in horses may be based upon the unique immunological makeup of the individual animal and his response to the vaccine. As such, the reaction is generally not due to a faulty or defective product. No horse responds the same to being vaccinated, which is why it’s very difficult to identify individual horses who are predisposed to allergic reactions. This is also why it’s important to involve your veterinarian.
Your Veterinarian’s Role
The relationship you have with your veterinarian is of tremendous value when making the best health-care decisions for your horse. It’s best to have your veterinarian administer vaccinations. He or she will be most familiar with your horse’s medical history, and well-versed in proper vaccine handling and administration techniques. — Duane E. Chappell, DVM, received his doctorate of veterinary medicine from Purdue University. In 2014, he joined the Merck Animal Health equine veterinary technical services team. Throughout his time in the field, he’s owned and managed solo and group practices, as well as being the resident veterinarian at Richland Ranch Quarter Horse breeding farm. After 27 years in the field, he became an assistant professor at Morehead State University in Kentucky.