What to Expect When Vaccinating Horses

vaccinationWe know you love your horse and understand that vaccinations can help protect it from life-threatening diseases. But vaccines can come with side effects due to the immune stimulation they have to create. Most of these effects are mild and transient, but it’s important to be able to distinguish between minor side effects and those reactions that warrant a call to your veterinarian.

“Keeping current with annual vaccinations as recommended by your veterinarian is the best way to help prevent potentially deadly equine diseases and help keep horses healthy,” says Megan Green, DVM, Manager, Large Animal Veterinary Services, Merial. “Equally critical is understanding that vaccines are designed to stimulate an immune response, and since your horse is unique, his specific response may be different from other horses.”

Normal Responses

After intramuscular vaccination, it’s fairly common for horses to experience mild, temporary side effects for a few hours. The American Association of Equine Practitioners lists these as:

– Local muscle soreness or swelling

– Fatigue

– Fever

– Loss of appetite

– Lack of energy or alertness

”Even humans experience signs like this following vaccination,” says Dr. Green. “These types of clinical signs help demonstrate that an immune response has been stimulated, which is exactly what we want the vaccine to do.” 
However, if the signs listed above last for more than 24 hours, you should consult your veterinarian as soon as possible to inform them of what is going on with the horse. This will allow your veterinarian to provide you with treatment advice and care instructions.

Causes for Possible Concern

Dr. Green cautions that sometimes more serious side effects, and in some cases, life-threatening events, can occur, including:

– Hives

– Difficulty breathing

– Collapse

– Colic

– Swelling at the injection site several days post vaccination.

”These more serious side effects are rare, but do require immediate consultation, and, in some cases, medical intervention.” 
Working with your veterinarian is the best way to ensure your horse is being evaluated based upon its particular needs. Many veterinarians follow the American Association of Equine Practitioners’ recommended guidelines for core vaccinations. Veterinarians can also be helpful in determining the need for other risk-based vaccinations based on an assessment of your geographic threats and travel plans. They are also familiar with the proper handling and administering of vaccines, which is important because those
handled improperly can actually become ineffective or may increase the risk of side effects.

“With many vaccines available online or through farm supply stores, some horse owners are purchasing and administering their own vaccines to try to save money,” Dr. Green says. “Because horse owners are not familiar with vaccine handling protocols, and how to handle adverse reactions should one occur, it’s best to partner with a veterinarian to ensure the horse is receiving the necessary vaccinations and the best overall health care.”

Staying Informed with Outbreak Alert

Besides working with a veterinarian to establish and implement an effective and appropriate vaccination schedule, you can also help protect your horse’s health by staying informed. Through Merial’s free Outbreak Alert program, reported cases of West Nile Virus, Eastern Equine Encephalitis, Western Equine Encephalitis, Equine Herpesvirus, rabies, equine influenza and Potomac Horse Fever are tracked throughout the country and noted on the Outbreak Alert maps at

The program also includes a free text and/or email notification system when threats are identified in the area surrounding entered ZIP codes. If you travel with your horse, you can enter multiple ZIP codes to help stay abreast of disease threats throughout the country. There are also veterinarian-exclusive features available through Outbreak Alert, including
 communication tools veterinarians can use in their practices. 
For more information, go to