It is a good idea to vaccinate the mother just prior to breeding. The mother's immunities will last between 8 to 12 weeks. So we begin vaccinating at 8 weeks in puppies and kittens. Some pets can actually begin as early as 6 weeks when we suspect the mother's immunities were weak. If we do not keep the vaccines spaced properly, vaccines given too soon will interfere with each other and vaccines given too far apart will not build upon each other.
Timing is critical.
The last vaccine must be given to the puppy at 20 weeks or older and the kitten by 12 weeks or older. This type of booster series will insure protection for the first year. So, the next time someone is presenting you with a new pet and they say it has had all its vaccinations, ask if it has received a series. If the puppy or kitten is only 10 weeks old, you know there are more vaccinations to come.