There’s no question that the discovery of vaccination is one of the most important advances in modern medicine. However, for all the good vaccines can do, like any other substance you put into a horse, they must be used intelligently.
With the huge variety of vaccines available, it’s easy to be drawn into the ”better give it just in case” way of thinking. Vaccines are indeed cheap insurance, but only if you need them. You wouldn’t buy flight insurance if you were never going to fly. Don’t buy vaccines your horse doesn’t need to receive, either.
Risks vs. Benefits
For most horses, the known risks from vaccinations are relatively small. Local reactions and a short loss of appetite and/or fever are a minimal price to pay for protection from a serious disease. However, many questions have been raised about less-tangible long-term effects on the immune system, especially with frequent vaccinations.
How significant these concerns are remains to be seen, but they probably have some truth to them. One thing is clear: Introducing a foreign substance into your horse when he doesn’t need it or it may not do what it is supposed to do is a risk without a benefit.
Common side effects after a vaccination are fever, local soreness or swelling, some loss of appetite, maybe even something as nasty as a vaccine-site abscess. These nuisances can occur in as many as 10% of vaccinated horses. However, there are other less-common reactions that are far more serious.
Severe allergic/anaphylactic reactions can occur in response to vaccines. These generally occur shortly after vaccination but, in rare cases, could be delayed for days or weeks. Rapidly occurring anaphylactic reactions are life-threatening and require the immediate administration of an antidote, usually epinephrine. This is one of the reasons we recommend always asking your veterinarian to do vaccinations.
Delayed reactions can take many different forms, from leg swelling to colic, to symptoms of the disease itself or sudden death. This has been poorly studied in horses, but it occurs in other species and people as well. This doesn’t mean that every time a horse gets sick after a vaccination you can blame the vaccine. However, you can’t automatically assume it isn’t vaccine-related either.
The best thing to do - besides getting veterinary care, of course - is to report any unexplained events to the USDA as possible vaccine reactions (see February 2003).
If no one else files a similar report, odds will be it wasn’t related. However, if people regularly reported things like this to the USDA, it will be a lot easier to pin down such problems, including oddities like a bad batch of vaccines.
We’ve listed in our accompanying chart (see below) our recommendations for equine vaccines. However, your veterinarian remains your best source in making the final decision. You need to know your horse’s risk factors for each disease and weigh them intelligently against the risks and benefits of the vaccine itself. You also need to consider your geographical location. A vaccination schedule is one place money shouldn’t be a signficant factor.
We also urge you to resist the temptation to purchase the vaccines and give them yourself. While it will save you money, the risk of your horse having a reaction is real - and you could lose your horse to a severe reaction before your veterinarian can even get out of his driveway.
In addition to the risk of losing your horse due to anaphylactic shock, for many of us, vaccine time is the only time our veterinarian gets a chance to see our horse, and reestablish ourselves as regular clients.
In some geographical areas where good equine veterinarians are few and far between, skipping the yearly vaccine barn call could leave you waiting a long time during an emergency when none of the area veterinary clinics have you listed as a regular equine client.