Early immunity induced by a glycoprotein E-negative vaccine for infectiousbovine rhinotracheitis

Four groups of calves were vaccinated with a glycoprotein E-negative vaccin e for infectious bovine rhinotracheitis. Two groups of calves were vaccinat ed intramuscularly and challenged with a wild-type virus 14 and seven days after being vaccinated. The other two groups were vaccinated intranasally a nd similarly challenged after four and three days; an unvaccinated control group was also challenged. All four vaccination schedules reduced the incid ence of clinical signs and the excretion of wild-type virus, and these redu ctions occurred as early as three days after the intranasal vaccination eve n in the absence of neutralising antibodies. Because of its marker characte ristics, vaccination with this vaccine would not interfere with the detecti on of infected cattle during an outbreak, and it should therefore provide a useful tool for emergency vaccination campaigns.