Abstract
Field trials were carried out to prove both the safety and the efficacy of a formalin-inactivated, oil-adjuvant-ed bovine coronavirus vaccine (BCV). The vaccine was prepared from BCV-infected cells solubilized with Tri-ton X-100 and mixed with an oil adjuvant. Eighty cattle, including38 pregnant Holstein-Friesian and F1, breeds, 1-6 months to 2-9 years of age, received2 intramuscular doses (2mleach) of the vaccine at 3-week inter-vals. Twenty other cattle were non-vaccinated controls. No adverse effects of vaccination on clinical manifes-tations and milk production were observed. Cows vaccinated during pregnancy gave birth to healthy calves in term. Vaccinated cattle developed high hemagglutination-inhibiting (HI) antibody titers, and the antibody lev-els thus attained persisted for 9 months. The geometric mean of HI antibody titers was 1: 54.1 at initial admin-istration. Three weeks later, the HI antibody titer rose to 1: 120.2 and reached a peak titer of 1: 674.2 1 month after the second administration. Nine months after the second administration, the HI antibody titer was 1: 180.6, indicating persistence of a relatively high-titered antibody. The field studies involved in this study prove the vaccine to be both safe and effective.
