Why do puppies need multiple vaccinations?
Most vaccines require multiple doses to be effective. Oral or intranasal Bordetella (Kennel Cough) and Rabies vaccines are two exceptions which are effective after a single dose.
Most common vaccines such as Lyme, Influenza, and Leptospirosis require two doses because the immune system response after the first dose is relatively weak. A second dose 2-4 weeks later will boost a pet’s immunity and provide much longer protection.
The DA2PP (Distemper, Adenovirus-2, Parvovirus, and Parainfluenza) vaccine provides protection against four illnesses. Unlike other vaccines, the first dose is started at 6-8 weeks old and must be boostered every 2-4 weeks until at least 16 weeks of age. This is done because puppies receive antibodies from their mothers (maternal antibodies) which supplement their weak immune system. These antibodies usually start to wear off around 6-8 weeks of age, which is when we start their vaccines. Though the antibody levels are declining, they are still present and interfere with the puppy’s immune system “remembering” the vaccine for more than a few weeks. That is why we keep boosting the vaccine until the antibodies are fully gone at 4 months of age.
This article has wonderful information on vaccines in dogs.
Conversation