Application of a chemically inactivated, adjuvanted vaccine to control abortigenic infection of mares by equine herpesvirus I.

A chemically inactivated, adjuvanted vaccine prepared from a virulent strain of Equine herpesvirus I (EHV-I) was used to immunize pregnant Thoroughbred broodmares during a five-year field test designed to determine its safety and efficacy. Each mare in the vaccinated groups received 3 intramuscular injections of vaccine beginning immediately prior to and during the last half of pregnancy. Vaccine was injected at approximately 60-day intervals. The accumulated incidence of EHV-I abortions among vaccinated mares during the field trial period was 1.6/1000 as compared with an incidence of 6.8/1000 in the remainder of the study population.