It seems like a simple process--uncap the needle, place it deep into the horse’s muscle, attach the syringe, pull back to ensure there is no blood, then inject 1-2 ml of material. This is what is commonly done when giving immunizations to a horse. Yet, this simply process relies on several factors in order for it to be done efficiently and to achieve optimum vaccine production.
First of all, it is essential that each vaccine is handled appropriately from its source at the manufacturer all the way to the moment of injection. Vaccines need to be maintained at specific chilled temperatures--even a short while without refrigeration can render them ineffective. Some require darkness for storage and will degrade if exposed to light. Often vaccines ordered on-line come from bulk suppliers with no guarantee that the product has been handled correctly at all times. On-line pharmacies also do not provide counsel or help in the event of an adverse reaction, but your veterinarian will. Purchase from a reputable source is essential if you insist on giving vaccinations yourself (which we don't recommend).
Secondly, knowing which vaccines to give for your local area and time of year is critical to providing appropriate immunization against disease risks. Your veterinarian is well versed in immunology and vaccine technology to understand the most effective program to keep your horse healthy and safe. Your vet also knows which pharmaceutical manufacturers are known for the fewest adverse reactions and which provide a vaccine product that is accepted well by horses. As a bonus, when your vet arrives to administer immunizations, she/he gives your horse the once over both visually and often with a physical exam, checking for anything off kilter. This is a good way to obtain early identification of subtle and not-so-subtle problems. This is also important to ensure you are giving vaccines to healthy horses that are capable of mounting an immune response to the vaccine that offers protection against disease exposure.
Next, if your horse is insured and you administer vaccines and the horse has an adverse reaction requiring veterinary care, will your insurance cover the claim? This is something you need to check with your insurance agent as every company has a different policy. It is possible that your claim might be denied due to owner administration of vaccines.
Despite these potential problem areas of owner administration of vaccines, nearly 50% of horse owners surveyed by the American Association of Equine Practitioners stipulated that they gave at least some of their own vaccines without veterinarian oversight, primarily due to cost considerations. There is a cost-benefit to everything, and it might well be that involving your veterinarian in immunization of your horse can actually save you money for all the reasons cited above. A known measure of safety and efficacy is better for your horse in the long run.