Parvovirus is probably the most common viral illness of dogs at
the present time. It is much more common in puppies than it is in adult
dogs. It can be very hard to successfully vaccinate a puppy for this disease
because the antibody protection the puppy acquires from its mother can
interfere with vaccination. It is important to vaccinate puppies every
three to four weeks for this virus starting at 6 weeks of age and continuing
until they are at least 16 weeks of age and preferably 20 weeks of age.
It is possible that this vaccine confers lifelong immunity once it does
work but most veterinarians continue to recommend every three year vaccination for
it. It seems prudent to at least get the vaccination at one year of age.