They can produce a good systemic immunity as well as a local immune response and can provide a more rapid onset of protection. For the lowest risk group of kittens, those in single pet homes, vaccination at eight and 12 weeks of age is appropriate. The earliest we can vaccinate a kitten in the highest risk situations is two weeks of age, since the lower body temperature of the neonatal kitten compromises its ability to mount an immune response before this. Vaccination before two weeks of age will provide little or no protection, and could possibly cause serious disease in some situations. We must also recognize that the ability of neonatal kittens to respond to vaccination varies greatly due to genetic and environmental factors that affect their immune system.
Various strategies are appropriate for catteries, including the use of IN vaccines.
Breeders who produce only one or two litters per year could use the protocol for the lowest risk group mentioned above. Larger catteries without serious URI problems could use an injectable MLV for FHV-1, FCV, and FPV at four weeks of age, with subsequent vaccinations at eight and 12 weeks of age. Catteries with a high level of endemic URI could use IN vaccines for FHV-1 and FCV at two to four weeks of age by administering one drop in each eye and one drop in each nostril per kitten. Good husbandry and isolation of kittens by age group are also very important factors in preventing disease in catteries. In general, IN vaccines without FPV and KV are safe in pregnant queens, but we must realize that there is some risk in using them, mainly connected to the possible occurrence of a vaccine reaction.