When considering at what age a puppy should begin receiving its core vaccines, consider the information from the American Animal Hospital Association stating that the maternal antibodies in a puppy younger than 16 weeks may interfer with the immune response. Bear in mind that there are risks associated with vaccinating as well as risks associated with not vaccinating. Making an informed decision is important. Also, be aware that giving combo vaccines (multi-valent) and/or several shots at once increases the risk of adverse reactions as well as the risk that the vaccines will interfere with each other, resulting in neutralization or negation.

On Page 16 of the of the American Animal Hospital Association's 2003 Canine Vaccine Guidelines, it reports that: When vaccinating an animal, the age of the animal, the animal's immune status, and interference by maternal antibodies in the development of immunity must be considered. Research has demonstrated that the presence of passively acquired maternal antibodies significantly interferes with the immune response to many canine vaccines, including CPV [parvo], CDV [distemper], CAV-2 [hepatitis] and rabies vaccines."

They further state on Page 17 that: "Multiple vaccinations with MLV vaccines are required at various ages only to ensure that one dose of the vaccine reaches the puppy's immune system without interference from passively acquired antibody. Two or more doses of killed vaccines (except rabies) and vectored vaccines are often required to induce an immune response, and both doses should be given at a time when the passively acquired antibody can no longer interfere. Thus, when puppies are first vaccinated at 16 weeks (or more) of age (an age when passively acquired antibodies generally don't cause interference), one does of an MLV vaccine, or two doses of a killed vaccine, are adequate to stimulate an immune response."

The AAHA Canine Vaccine Guidelines also declare on Page 17 that: "If a pup fails to respond, primarily due to interference by passively acquired maternal antibody, it is necessary to revaccinate at a later time to ensure adequate immunity."

On Page 13 of the 2006 American Animal Hospital Association's Canine Vaccine Guidelines, it lists as the most common reason for vaccination failure is "the puppy has a sufficient amount of passively acquired maternal antibody (PAMA) to block the vaccine......" They elaborate by reporting that at the ages of 14 to 16 weeks of age, "PAMA should be at a level that will not block active immunization in most puppies (>95%) when a reliable product is used."

Combination Vaccines, Multiple Shots--on Page 16 of the 2003 AAHA Guidelines under Immunological Factors Determining Vaccine Safety, it states that: "Although increasing the number of components in a vaccine may be more convenient for the practitioner or owner, the likelihood for adverse effects may increase. Also, interference can occur among the components. Care must be taken not to administer a product containing too many vaccines simultaneously if adverse events are to be avoided and optimal immune responses are sought. "

The World Small Animal Veterinary Association's 2007 Vaccination Guidelines state on Page 3 that: In situations where, for example, a decision must be made that an individual pet may have to receive only a single core vaccination during its lifetime, the VGG [Vaccination Guidelines Group] would emphasise that this should optimally be given at a time when that animal is most capable of responding immunologically, i.e., at the age of 16 weeks or greater."

If anyone would like copies of the American Animal Hospital Association's Canine Vaccine Guidelines, the 1992 French challenge study demonstrating that dogs were immune to a rabies challenge 5 years after vaccination, the 2003 Italian study documenting fibrosarcomas at the presumed injection sites of rabies vaccines in dogs, as well as Dr. W. Jean Dodds' papers on vaccinal adverse reactions, please e-mail me at [email protected].

Duration of Immunity to Canine Vaccines: What We Know and Don't Know, Dr. Ronald Schultz

World Small Animal Veterinary Association 2007 Vaccine Guidelines Scroll down to Vaccine Guidelines 2007 (PDF)

The 2003 American Animal Hospital Association's Canine Vaccine Guidelines are accessible online at .

The 2006 American Animal Hospital Association's Canine Vaccine Guidelines are downloadable in PDF format at .

Veterinarian, Dr. Robert Rogers,has an excellent presentation on veterinary vaccines at