Vaccinating adult dogs: every year or every three years
Healthy 4-year-old Labrador that has received distemper, adenovirus, parvovirus and Leptospira vaccines every year. It walks in the countryside and swims in ponds.
Which revaccination schedule is appropriate?
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A. All of them every 3 years, because it is a well-vaccinated adult dog
Immunity against Leptospira is short (about a year) and serogroup-specific; spacing it to 3 years would leave the dog unprotected.
B. Distemper, adenovirus and parvovirus no more often than every 3 years; Leptospira every year
Correct. Modified-live core vaccines induce immunity lasting many years, so WSAVA recommends not repeating them more than once every 3 years. Bacterins such as Leptospira need an annual booster.
C. All of them every year: annual revaccination is never harmful
Vaccinating more than necessary adds no extra protection and needlessly exposes the dog to the risk, albeit low, of adverse reactions.
D. Stop vaccinating: after several doses the dog is protected for life
Although immunity to the core viral diseases is long-lasting, lifelong protection cannot be assumed for every dog, and Leptospira immunity wanes within a year.
lightbulb Key takeaway
The three-year interval refers to the vaccine, not the visit: the annual health check remains. Check that the product's licence includes a 3-year duration of immunity, and remember that rabies follows regional regulations.
References: WSAVA Vaccination Guidelines 2024
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.