There is one vaccine approved for use in horses in the united states it is a killed vaccine and is labeled for use in healthy horses 6 months of age or older duration of immunity of this product has not been determined vaccination will prevent animals from shedding leptospiral organisms in urine horses 6 months of age or older should receive two initial doses 3 4 weeks apart with annual revaccination the product can safely be used in mares up through the second trimester of pregnancy. Vaccination for animal health an overview summary vaccination has long been an effective way to reduce disease burden in pets and farm animals and is a key tool in maintaining animal health and welfare vaccines continue to play an increasingly vital role in preventative health and disease control programmes in animals innovative research and the development of safe effective and quality vaccines means that our pets and farm animals continue to benefit from vital medicines that prevent . Core vaccines are those that are recommended for administration to every animal based on 1 universal susceptibility to disease caused by a specific infectious organism 2 significant risk that animals in the area will become infected 3 likelihood of significant medical consequences to the animal as a result of infection and disease 4 availability of a vaccine that is both safe and highly effective and 5 possible risk of zoonosis in other words core vaccines are those for . Title page of martins on animal vaccination 1878 description boston physician henry austin martin brought what he called true animal vaccine material produce by inoculating a calf with cowpox lymph to the united states in 1870 in this article he describes how he procured the animal vaccine from the beaugency strain developed in france