The efficacy of a multivalent, modified-live virus vaccine containing canine adenovirus (CAV) type-2, canine parvovirus (CPV), and canine distemper virus (CDV) was evaluated with a challenge-of-immunity study. Seronegative pups were vaccinated at 7 and 11 weeks of age or served as controls. All animals were kept in strict isolation for 3 years after the last vaccination. The dogs were then challenged sequentially with virulent CAV type-1, CPV, and CDV. For each of the viral challenges, a separate group of age-matched control dogs was also challenged. The CDV challenge was also done on seronegative pups. The test vaccine included the Manhattan strain of CAV-2, which confers cross-protection against canine infectious hepatitis caused by CAV-1; high-titer patented CPV STRAIN 154; and a high-titer Onderstepoort strain of CDV. The vaccine also contained canine parainfluenza.

Clinical signs were prevented in 100% of the vaccinated dogs while control dogs and pups exhibited signs and some died. The vaccine met or exceeded the Code of Federal Regulations (9 CFR) for efficacy in protecting against virulent CAV-1, CPV, and CDV challenges. This study provides sound justification for current scientific thought and recommendations for changes in vaccination protocols from once yearly to every 3 years. Study supported by Intervet

Three-year duration of immunity in dogs following vaccination against canine adenovirus type-1, canine parvovirus, and canine distemper virus. Gore TC, Lakshmanan N, Duncan KL, et al. VET THER 6:5-14, 2005.