Does modified-live viral vaccine administration to heifers or cows lack substantial risk?

Abstract

Modified-live viral (MLV) vaccines are an important tool to limit reproductive loss subsequent to infection from bovine viral diarrhea virus and bovine herpesvirus-1, but are not without risk. Therefore, their utilization must be undertaken with an understanding of the inherent risks of the vaccines and their administration. These risks include the potential causation of undue harm and lack of effective immunization. Consequently, vaccine programs should be designed to minimize the risks while maintaining or maximizing potential benefits of vaccination. The risk of viral transmission from vaccinated calves to naive cows is low but not absent. Therefore, cows and heifers should be effectively immunized prior to gestation, ideally at least 30 days before breeding. Additionally, revaccination of pregnant cows previously vaccinated with the same MLV vaccine carries a low but detectable risk of adverse reproductive consequences. Understanding the level of risk associated with the vaccination of cattle against bovine viral diarrhea virus and bovine herpesvirus-1 will aid in the optimization of vaccination protocols. Proper timing of MLV vaccine administration can maximize protection against reproductive viral pathogens while minimizing the potential for the development of adverse consequences subsequent to vaccination.