Are We Over-Vaccinating Our Horses?


A to-the-point discussion with Dr. Dennis Rach of Moore Equine Veterinary Clinic, Balzac, Alberta.
Q. Recently there appears to be a fair amount of literature surfacing on the internet regarding the potential “over-vaccination” of our horses. Can you comment on this at all?

DR – There are people who have decided that vaccines are poison, etc. The fact is that influenza vaccine is only effective for a period of time. Intramuscular influenza vaccine elicits an immune response that elevates the antibody level to a point above the known protection level for a little over six months.  That is why show horses should need two flu shots a year. Since most flu cases appear in the spring and not the fall, we usually vaccinate in the spring to be able to give it to horses just before they start to go out and come into contact with others.

Rhino is somewhat the same but the protective immunity level is “somewhat protective” for two or three months. The reason we give the rhino vaccines at stables is because we think it reduces virus shedding by carrier animals. Mosquito-borne virus vaccines elicit protection for 10 to 12 months and so annual vaccination is adequate.

Potomac horse fever (PHF) vaccine is given twice a year in endemic areas but in Alberta we only see it from August through October and so we vaccinate high risk areas for PHF late spring or in the summer. There is more PHF found east of Calgary in the irrigation areas than west of the city, so many people west of Calgary do not vaccinate. They feel the incidence is low enough to take the risk of not vaccinating.

Strangles vaccination seems to be protective against the Strep-equi strain for around 10 months and so we also do it annually.  However, if a horse gets the disease naturally and recovers from Strangles, the affected horse usually has protection against the disease for three years or so. Therefore, these horses do not need immunization during that time. The death rate in a stable with a strangle outbreak on average, is around 3 to 5% of that population.
Tetanus and rabies are effective for several years so if the tetanus toxoid was not already in the sleeping sickness vaccines, we would not vaccinate for it but every four or five years.

In short, most of the respiratory vaccines do not elicit a lengthy enough response to be protective for more than a year. After that time period, horses who have been challenged with live virus get sick. Clinical trials on vaccines have been done to determine the degree of protection – their purpose is to essentially work out vaccination protocols and discover how often we have to vaccinate, to achieve and maintain protection.

* Be sure to check out the upcoming April issue of Western Horse Review! In it you will find a comprehensive article on vaccinating your horses for 2013.


7 thoughts on “Are We Over-Vaccinating Our Horses?”

  1. Thanks for the info. Dr. Rach didn’t address the vaccines for Sleeping Sickness, West Nile or Tetnaus. We are vaccinating once a year and some Dr.’s are saying that is too often. What is his response to this? And does he recommend yearly vaccinations or would it be adequate to vaccinate every other year.


    Carola Friesen

  2. I apololgize, I just reread the article and realized I missed some pieces of it. I read here that he recommends annual vaccinations,. Thanks for the info.

  3. We know we ARE overvaccinating our dogs – I would think the horses would be similar, it may just take a few more years to have an actual study (like we have for dogs) done that proves this. Some things only need to be done once in the lifetime of the animal – we need more concrete evidence at this point to prove it in horses. We do have an actual 7 year study in dogs that proves this.

  4. Instead of over- vaccinating (vaccinating more than what is suggested by Dr. Roch) our horses (or dogs for that matter) why not use herbs to help boost your horse’s immune system ?? If a horse has a strong immune system the chances of getting sick are drastically decreased, as the immune system is what fights off foreign invaders in the body. If you boost the immune system before you take them out to compete or if they are around potentially sick horses this will give them a much greater chance of staying healthy and performing at their best.
    Omega Alpha Pharmaceuticals (found in many feed stores) carries some great immune boosting formulas. Also, consider giving your horse a good mineral to keep the body and organs functioning at their best and a good probiotic (Omega Alpha’s Biotic 8)- a healthy gastro- intestinal system = healthy immune system. Probiotics help to break food down and allows the body to absorb nutrients better. Proper nutrition for your horse directly relates to the immune system.
    Trying to eliminate as many un-necessary forms of stress and possibly including a form of equine therapy is another excellent way to keep your horse balanced and healthy.
    If your horse is balanced, healthy, and you help boost the immune system in times where the body may become more stressed the need to “over vaccinate” should not be an issue !!

  5. What is not addressed at all is why vets are not making clients aware of and offering titre tests (which give you an indication of the animal’s current level of protection and thus whether or not additional vaccination is required at this time) at a reasonable cost. They currently cost more than the shots (if you can find a vet who is willing to do them for you) but would help concretely identify if you need them at the time AND prevent any possible “over vaccination” issues.

  6. To vaccinate or not to vaccinate … a dilemma for most animal owners. The cost of veterinary care for an animal that has caught a disease can end up in the thousands of dollars. The cost of vaccinating is approx $100 (for 6-way once per year) and $35 more for intra-nasal strangles. We only have a few horses so an easy decision for us, vaccinate them all. The 2 that don’t leave the farm get 5-way and the 2 that leave the farm for events get 6-way and strangles. A much harder decision for people that have many horses. I guess when I ask myself the question “Are we over-vaccinating?” I just think about the consequences of under-vaccinating ….

  7. There are actually more risks involved with “over-vaccinating” than there are of “undervaccinating”. We are just not made aware of all the risks involved with vaccines and sometimes we don’t connect an illness to a vaccine because it doesn’t always happen immediately afterwards.

    Vaccination does not equal immunity. Some animals do not respond to the vaccine and unless we do a titer test we will not know that, therefore, they could be vaccinated and have all the risks involved with a vaccine plus still have the risk of getting the disease.

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