Safety and Efficacy of Viral Vaccines for Bovine Reproductive Pathogens

When considering safety and efficacy in the context of viral vaccines for bovine reproductive pathogens, safety is considered to be the lack of post-vaccinal adverse events for the vaccinated bull, heifer or cow and the associated semen, oocyte, zygote, gestating embryo, developing fetus, and newborn calf; efficacy is considered to be the resulting protection of health after post-vaccinal exposure to the pathogen of the vaccinated sire or dam and the associated semen, oocyte, zygote, gestating embryo, developing fetus, and newborn calf.

As bovine viral diarrhea virus (BVDV) and bovine herpes virus-1 (infectious bovine rhinotracheitis [IBR] virus; infectious pustular vulvovaginitis virus) are the most common viral pathogens impacting bovine reproduction in the United States, the safety of BVDV and IBR viral vaccines will be the primary focus of this manuscript. While some serotypes of bluetongue virus (BTV) do cause reproductive loss in cattle in the United States, the impact of currently circulating North American serotypes are frequently subclinical;1,2 thus, the perceived need for immunization of cattle in the United States with BTV is currently very low. Modified-live vaccinal strains of BTV can clearly be acquired and transmitted by insect vectors.1 Strains of BTV in modified-live vaccines also exhibit the capacity to cross the placenta and infect the bovine fetus resulting in a teratogenic outcome. Inactivated BTV vaccines approved for use in cattle exhibit little if any commercial availability in the United States. The relatively slow onset of immunity compared to modified-live vaccines and the necessity of serotype-specific vaccine formulations negatively impacts the potential commercialization of inactivated BTV vaccines based on the current ecology of this non-zoonotic pathogen in the United States.1 […]