An adult dog ages faster than a person, by approximately 4 to 1 (the first year for a dog is about 20 for a person). The same goes for cats.
Some vaccinations in dogs are effective for 3 years - Rabies, Distemper, Parvovirus. Others aren’t effective that long - Leptospirosis (which are transmissible to people), Bordetella, Influenza (canine strains). The annual examination is also equivalent to the recommendation that adult humans have a physical every 5 years.
Feline vaccinations also vary – some Rabies vaccines are good for one year, others for three. The Distemper/Upper Respiratory combination (FVRCP) is good for three years in adult cats. Feline Leukemia needs to be boosted annually.
The American Animal Hospital Association and The American Association of Feline Practitioners work with veterinary researchers, specialists, and both industry and general practitioners to update recommendations for vaccination frequency.
You still need that annual exam. We catch many health problems before they even become a problem, and it provides you an opportunity to ask any questions about your pet and health.