Canine and feline vaccines have been available for many years, but they continue to improve in quality and expand in number and types available.  Canine and feline vaccination guidelines have been developed by species specialty groups.  The two basic types of vaccines include 1) infectious and 2) non-infectious.  Vaccines vary based on the specific diseases of the country or regions within the country.  Vaccination programs are similar worldwide, in part due to the World Small Animal Veterinary Association (WSAVA) Vaccine Guidelines.  The WSAVA Guidelines for the cat are similar to the feline guidelines of the American Association of Feline Practitioners (first in 1998, updated in 2000, 2006, and expected for 2012).  Similarly, the WSAVA Canine Vaccine Guideilines are similar to canine guidelines developed by the American Animal Hospital Association (AAHA) (first in 2003, updated in 2006 and 2011).  Vaccines for both species have been categorized based on need.  Core vaccines are those that every cat or dog should receive, whereas the non-core (optional) vaccines are based on a risk/benefit analysis.  The general vaccination recommendations for the cat and dog are to begin the vaccination program with the core vaccines at approximately 6 weeks.  Revaccination should occur at 2 to 4 week intervals, with the last dose of vaccines at 14 to 16 weeks of age.  Non-core vaccines can be given during this time or after the completion of the core, or not at all.  Revaccination with core vaccines is then recommended by the first year of age, followed by revaccination every 3 years or longer.  Most non-core vaccines must be given annually.