Serologic response of pups to the low-passage, modified-live canine parvovirus-2 component in a combination vaccine.

Thirty pups from a general pet population were vaccinated for canine parvovirus-2 (CPV-2), using a low-passage, modified-live CPV-2 in a combination vaccine, every 3 weeks until the pups were between 11 and 18 weeks old. Canine parvovirus-2 antibody titers were measured by means of serum neutralization (SN) immediately before each vaccination and > or = 2 weeks after final vaccination. Thirteen pups that were initially seronegative (SN titer < 2 for CPV-2) developed protective titers (SN titer > or = 16) after 1 to 3 doses of the vaccine, administered when the pups were between 8 and 17 weeks old; 11 of the 13 developed protective titers after the first dose. Seventeen pups were initially seropositive for CPV-2 (SN titer > or = 2). Of these, 8 initially had titers < 16 and 3 others had titers that fell to < 16 during the study. Nine (82%) of these 11 pups developed protective titers. Results indicated that pups at high risk for CPV-2 disease should be vaccinated until 18 to 20 weeks old, even when the low-passage vaccine is used. Pups at lower risk of CPV-2 disease should be vaccinated periodically until 16 weeks old.