Early immunity induced by a glycoprotein E-negative vaccine for infectious bovine rhinotracheitis.

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