Dogs, like cats, acquire their initial immune system via breast milk in the first hours of life. This special milk, called “colostrum”, contains molecules (“maternal antibodies”) developed by the mother as a result of her vaccinations and disease exposures. Maternal antibodies alert the puppy’s immune system to the presence of harmful organisms, but get removed from the system over time. Maternal antibodies may be cleared from the system anywhere between 6-16 weeks of age, and block the effectiveness of vaccines when present in large numbers. For this reason, it is important to have your pet vaccinated with core vaccines (except rabies) beginning at 6 weeks of age and then every 3-4 weeks until 16 weeks of age. Regardless of age, some vaccinations are most effective when given as a two-injection series 3-4 weeks apart (called a booster). In order to avoid inactivation by maternal antibodies, the rabies vaccine must be administered after 4 months of age. Not vaccinating your puppy within the first 8 weeks of life may allow the opportunity for life-threatening illness to develop.
When to Re-vaccinate Dogs
Scientific studies have demonstrated that some vaccines are effective up to 5 or more years, despite manufacturer recommendations of annual vaccination. Re-vaccination should be considered in light of the risk inherent to an immune-system challenge. To balance the risk of a vaccine becoming ineffective over time and the risk of adverse vaccine reactions, many authorities recommend re-vaccination every 3 or more years for rabies, DA2PP, and most non-core vaccines. One important exception is Bordetella (kennel cough), which protects for up to 6 months if given intranasally (preferred route) or up to a year if injected under the skin. The latter is less effective unless preceded by an intranasal form of the vaccine. A second exception is the Leptospirosa vaccine, which is generally considered to protect for up to a year.
When Not to Vaccinate Dogs
Like cats, vaccinations should never be administered to your dog if he or she is sick, immunocompromised, receiving immunosuppressive medications, or has an ongoing infection. Doing so may block the effectiveness of the vaccine, lead to more serious side effects, and/or worsen the current problem. In order to reduce the risk of adverse reactions, the number of vaccinations performed at one time should be limited as much as is reasonable. No vaccination should be given without a thorough physical examination being performed by your veterinarian. The most appropriate vaccination schedule for your pet can only be determined by discussing your pet’s age, lifestyle, and state of health with your veterinarian. Of course, applicable government legislation must also be considered.
This article is a summary only. Recommendations vary depending on individual and location factors. The following links contain additional information that may be useful in your discussions with your veterinarian.
2010 World Small Animal Veterinary Association canine and feline guidelines.