Vaccinations trigger the immune system to produce antibodies against specific viruses or bacteria that cause disease. Puppies and kittens typically receive their first set of vaccinations when they are between 6 and 9 weeks of age. They will then return for boosters every 3 weeks until they are 16 weeks old.
In the first few weeks of life, puppies and kittens receive protective antibodies from their mothers, but over time these antibodies will wear off and their immune systems will need to start making antibodies on their own. While the maternal antibodies are present, they not only protect against infection from disease, they also will prevent the animal’s immune system from responding to a vaccination. Maternal antibodies wear off at a different time in every individual, anywhere between about 6 and 16 weeks of age and there is no way to tell when this occurs. Giving multiple sets of vaccinations during the early months of life is the best way to ensure your puppy or kitten will be protected from life-threatening diseases.