A foal’s protection against infectious diseases begins before birth. Vaccinating a pregnant mare four to six weeks prior to foaling helps her pass critical maternal antibodies on to her foal within the first 12-24 hours of his life. These maternal antibodies provide future immune protection to the foal, but they can also interfere with or inhibit his ability to respond to vaccinations. Specific antibody levels decline at various times during the first six months, so the owner and veterinarian need to establish a timeline for administering the various vaccinations. Foals born to unvaccinated mares generally need to be vaccinated earlier because they do not have the same level of antibody protection.

The American Association of Equine Practitioners has developed guidelines for foal vaccinations that include core and risk-based vaccines. (For specific vaccine dose recommendations, see www.aaep.org/vaccination_guidelines.htm.) Core vaccines have been proven effective and safe; therefore, they pose low enough risk and high enough benefit to be recommended for all foals. The core vaccines include those designed to protect against tetanus, Eastern/Western equine encephalitis (EEE/WEE), rabies, and West Nile virus (WNV).

The tetanus vaccination has been proven very effective in protecting foals from a disease that can often be fatal. Foals of vaccinated mares should receive their first of three tetanus vaccines at 4-6 months, whereas foals of unvaccinated mares should begin their three-dose series at 1-4 months.

Eastern and Western equine encephalomyelitis are fatal diseases caused by mosquito-borne viruses. Foals born to vaccinated mares should get their first EEE/WEE vaccine at 4-6 months, although those born in the southeastern United States and other areas where mosquito vectors are present year-round should have their initial dose at 3 months. Foals born to unvaccinated mares should have an initial dose at 3-4 months