The results indicated that vaccination at 4 weeks of age in pups with high levels of maternally derived antibodies produces seroconversion rates that may lead to a reduction in the susceptibility window with respect to CPV infection. Shelters usually vaccinate puppies for the first time at four or six weeks of age. At four weeks, puppies' immune systems are barely mature enough to develop antibodies after exposure to disease antigens; this is done in an effort to immunize puppies that did not receive any maternal antibodies as soon as possible. The purpose of vaccines for puppies and dogs is to slightly stimulate the immune system by making it recognize the antigens present.
Once your puppy reaches adulthood and all major puppy vaccinations have been given, your veterinarian can begin implementing a vaccination schedule for adult dogs. With that said, here is a generally accepted guide to the puppy vaccination schedule for the first year. If you plan to ship your puppy in the future, attend group training classes, or use dog day care services, a test of this vaccine will often be required. The first rule for vaccinating puppies is that there are no hard and fast rules for vaccinating puppies; the best way to ensure that a puppy is fully immunized against the most common contagious diseases depends entirely on the health and history of the puppy's mother, her age and her environment.
Regular vaccinations help puppies become dogs that remain free of infectious diseases and also prevent them from transmitting unpleasant diseases to other animals. Therefore, puppies need a series of vaccines to allow their immune system to “break down the maternal antibody decline.” In general, a puppy should start getting vaccinated as soon as they receive the puppy (this is usually between 6 and 8 weeks) and then every two weeks until about four months of age, when they will receive the last round. If an unvaccinated dog contracts and then survives a disease such as parvovirus, it actually develops a much stronger immunity to the disease than if it had been vaccinated against the disease in the first place, and it will transmit this very robust protection to its puppies (provided they receive an adequate amount of colostrum). The vast majority of puppies will be successfully immunized after the series of vaccines described here, but a small percentage will be what are called “non-responders,” unable to develop protective antibodies in response to vaccines.
A puppy raised by a responsible breeder may require only one combination vaccine to be vaccinated; whereas a puppy raised in a shelter may receive up to six or seven combined vaccines before being declared fully protected. Most veterinarians recommend that puppies get vaccinated against distemper, parvovirus, and adenovirus (hepatitis) several times, starting when they are around four to six weeks old, and again every three to four weeks, with their last “puppy” vaccine given after they are between 16 and 20 weeks of age age. They had had 2 rounds of shots, but it clearly wasn't enough to protect these 3 puppies (outside of So I bleached every conceivable surface to kill the virus.