JMO
From, what I understand, the reason for giving them 3 shots is because the immunity they get from the mother loses it's protectiveness at different times, depending on a variety of factors. But somewhere between 9 and 16 weeks.
Any shots given while the puppy is still protected by the mothers immunity is render useless. So they give the shots at 3 week intervals to assure they are protected.
However, all of the mother's immunity should be out of their system by 16 weeks, therefore the shot at 16 weeks should be all they need, and any shots after 16 weeks are unnecessary.
Again, this is just my understanding. |