To be fully protected, puppies require a series of vaccinations. Vaccinating puppies once, or even twice may not protect against disease. That is because nursing puppies get antibodies via the milk from their mom. Antibodies, although great for protecting puppies against disease, cancel out the protection that vaccination provides.
Because we don’t know if maternal antibodies are present when we vaccinate, we give vaccinations to puppies and kittens, every 3 to 4 weeks, until puppies reach the age that maternal antibodies are no longer in their system. That age is usually about 16 to 18 weeks of age for their last vaccination.
It is important to follow the schedule outlined by your veterinarian. Vaccination series are modified depending upon the age that a puppy was started on its first vaccination. Making sure your puppy or kitten gets all of its series of vaccinations is the best way to protect them from disease.