Protection afforded by vaccination is not necessarily life-long. The duration of immunity varies depending on the circumstances of the individual animal and the vaccine used. Long-term protection afforded by vaccinations varies according to the manufacturer and the antigens contained. For example, leptospirosis vaccines can provide adequate protection for less than a year in most animals. Protection against diseases can now be achieved by giving many of the other vaccines at intervals of 2 or 3 years. This varies according to the disease for which protection is required and the brand of vaccine used so ask your vet to explain the specific requirements for your pet.