Alternative early life vaccination programs for companion animals.

An experimental challenge study of multicomponent vaccination of kittens is reported. Seven-to-nine week old, specific pathogen-free kittens received two injections (4 weeks apart) of non-adjuvanted, multicomponent vaccine formulated at the minimum protective dose. Kittens were challenged at 4 weeks or 1 year post-vaccination with individual infectious agents. Vaccination induced complete protection against challenge from feline parvovirus on both occasions, but at 1 year, the protection against feline herpesvirus, feline calicivirus and Chlamydophila felis was not as strong as 4 weeks after vaccination. This demonstration of a decline in protective immunity at the normal time of administration of the first booster vaccine suggests that earlier administration of this booster (at 4-6 months of age) may provide better protection. The effect of maternally derived antibody (MDA) on kitten vaccination was determined by conducting an identical experiment but with kittens born to queens vaccinated during pregnancy. Serum antibody titres to specific vaccine components were measured in these kittens on day 0 (time of first vaccination), day 28 (time of second vaccination) and day 42. There was heterogeneity in transfer of MDA to kittens within a litter, and between litters. MDA may neutralize the serological response of kittens on the first, and occasionally the second, occasion of vaccination when vaccination is performed at 8 and 12 weeks of age. This finding underpins recent recommendations that the final vaccination in the primary series be administered at 16 weeks of age.