What is the earliest age at which an animal can be safely vaccinated?
In general, six to nine weeks is the earliest age at which a routine vaccination program should be started. Exceptions occur for animals who are in environments which would likely expose them to disease, e.g., humane shelters, breeding facilities, etc. These animals may benefit from earlier vaccinations. Vaccination with a parvovirus vaccine in puppies 5 weeks of age is recommended by some. Vaccinating puppies and kittens less than 4-5 weeks of age, especially with modified live vaccines, can cause severe problems.
