Assessment of the efficacy of a single dose of a recombinant vaccine against West Nile virus in response to natural challenge with West Nile virus-infected mosquitoes in horses.

Objective: To determine the onset of immunity after IM administration of a single dose of a recombinant canarypox virus vaccine against West Nile virus (WNV) in horses in a blind challenge trial.

Animals: 20 mixed-breed horses.

Procedure: Horses with no prior exposure to WNV were randomly assigned to 1 of 2 groups (10 horses/group).