Overview BOVILIS® GUARDIAN® is a multiple-antigen product shown to be effective for the vaccination of healthy pregnant cattle to provide passive immunity against neonatal calf diarrhea caused by enterotoxigenic E. coli pilus type K99, bovine Group A Serotype G6 and G10 rotaviruses, bovine coronavirus types 1 and 3, and enterotoxemia caused by Cl. perfringens Types C and D.