Foal Vaccinations
By Dr. Paula Valeria

Foal vaccinations or immunizations are a very important part of an infectious disease prevention program for your growing baby. However, the immune system and how it responds in these little ones is quite complex. The age of the foal, whether or not its mother was vaccinated prior to foaling, whether or not it received and absorbed adequate colostrum, the management situation, the exposure risk, and the region of the country the foal resides all play a role in determining which vaccines should be given and when they should be administered.

The colostrum that your foal received from its mother just after birth has helped provide the initial protection it needed in the first months of life. However, these protective antibodies decline with time leaving your foal susceptible to infection. These same “maternal antibodies” interfere with vaccines by preventing the desired immune response, even when they are below protective levels.

This makes it very difficult to time the initial vaccines so that they are effective but yet administered early enough so to not leave the foal unprotected as maternal antibodies wane.  The duration of maternal antibodies varies with individual foals and with different infectious agents. The maternal antibodies of foals to many infectious agents fall to non-protective levels by about 2-3 months of age, but may prevent a response to a vaccine for weeks or months to come.  Influenza or Flu has been shown to have some of the longest maternal antibodies which persist up to 6 months of age.

Although it is impossible to make universal recommendations for foal vaccination, with these factors in mind we can come up with some guidelines. In general, foals from mares who have been vaccinated prior to foaling should be starting their vaccines at 4-6 months of age.  Foals of unvaccinated mares should start at 3-4 months of age.  It has also been recommended in recent years to give a series of three vaccines to foals. The 3-dose regime was shown to produce a better immune response than a 2-dose regime, so this is the current recommendation for most of the vaccines. 

Your veterinarian should help you develop a vaccine protocol for your particular foal or farm. Along with vaccination, decreased exposure to pathogens, elimination of foal stressors that decrease resistance and maintenance of optimal nutrition are essential to preventing infectious disease.

For more information on foal vaccination recommendations based on the American Association of Equine Practitioners guidelines, visit Great Lakes Equine Wellness Center’s website at www.glequinewellness.com/education.html. Remember your veterinarian should help you develop a vaccination program that fits your individual situation.