Vaccines: What, Why, How & When?


A vaccine is a substance containing a non-infectious form of a virus for bacteria that is given to an animal to prevent disease or lessen symptoms of disease if the animal is ever infected with that particular virus or bacteria.


Many diseases are caused by virus & bacteria. These diseases can be quickly and easily spread among animals and people. Vaccination helps to prevent or decrease the likelihood of spreading disease by stimulating the body’s immune system to produce antibodies against the disease-causing agent that protect and prevent the animal from getting sick or dying. In the horse, the classic example is Eastern Equine Encephalitis (EEE). EEE is a fatal disease caused by a mosquito-borne virus that horses can get from birds. The virus causes “sleeping sickness,” a high fever followed by neurological signs, eventual paralysis and death. Annually, there are fatalities in Florida in unvaccinated horses. While EEE is generally something we vaccinate for in the spring, the same science applies for RabiesRhinopneumonitis and Influenza, which are the vaccinations recommended for the fall. 


A vaccine is made by changing a virus into a harmless form, then adding a chemical agent called an adjuvant which assists in the absorption of the vaccine from the injection site. Vaccine companies do substantial testing of these viruses because of their ability to change (mutate) which then requires a change in the makeup of the vaccine in order for it to be effective. Occasionally, a horse will have a sore neck or fever after a vaccination referred to as a reaction. This is temporarily uncomfortable to the horse but not harmful, and certainly better than the horse going unvaccinated. Please call your veterinarian if you notice a reaction in your horse. In spring of 2016, we were lucky to experience a 0% vaccine reaction rate among our patients, and we anticipate the same this fall. In the case of a reaction, your veterinarian will likely recommend banamine as an anti-inflammatory. 


In Colorado, naturally occurring respiratory disease in horses happens in September. It takes two weeks for an administered vaccine to become effective in the horse’s body. Because of this, we recommend that your horse be vaccinated in late August or early September. 

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