It takes 2 vaccines for a puppy or a dog to develop immunity, provided that the maternal antibodies that a pup gets from the mother dog are gone from their system. The maternal antibodies disappear from the pups anywhere from 6-12 weeks of age.
Vaccines given to a puppy that still has active maternal antibodies are destroyed by those maternal antibodies (MA) and do nothing to build immunity in the pup. It's too expensive to test each puppy for active MA, so vaccination is started anywhere from 6-12 weeks of age.
Some pups lose their MA at 6 weeks of age, and will benefit from the vaccine and develop their own antibodies. Some pups won't lose their MA until 12 weeks of age, and will need 2 more vaccines to develop immunity. |