Vaccinations, starting by 8 weeks of age, will prevent
most (but not all) cases of parvovirus infection. During the first weeks of
life, puppies are protected by high levels of maternal antibodies. As these
levels decline, there is a period lasting from two to four weeks during which
puppies are susceptible to infection because vaccinations have not yet fully
taken effect. This susceptible period varies from pup to pup, which is why pups
anywhere between 6 and 20 weeks age can be especially susceptible to parvo.
Nearly all apparent vaccination failures are due to exposure during this
Newer high titer-low passage vaccines are narrowing the window of
susceptibility. These modified live virus vaccines contain a higher number of
virus particles (high titer), which are less attenuated (low passage; a low
passage vaccine contains virus particles that have been less attenuated, or
weakened, than those in the average vaccine). That means high titer-low passage
vaccines can generally elicit an immune
system response in young animals who have a maternal antibody level that
would normally prevent them from responding.
Nevertheless, it is still important to isolate young puppies as much as
possible from other dogs and from potential sources of infection until they
complete the parvo vaccination series at 16 weeks of age.
Currently, recommendations are for a booster a year from the initial vaccine
series and then revaccination every three years.