Here's the guide for US vets from the AAHA:
Vaccines should not be given needlessly. Core vaccines should not be given any more frequently than every three years after the 12
month booster injection following the puppy/kitten series, because the duration of immunity (DOI) is many years and may be up
to the lifetime of the pet.
The VGG has defined non-core vaccines as those that are required by only those animals whose geographical location, local
environment or lifestyle places them at risk of contracting specific infections. The VGG has also classified some vaccines as
not recommended (where there is insufficient scientific evidence to justify their use) and has not considered a number of minority
products which have restricted geographical availability or application.
The VGG strongly supports the concept of the ‘annual health check’ which removes the emphasis from, and client expectation of,
annual revaccination. The annual health check may still encompass administration of selected non-core vaccines which should be
administered annually, as the DOI for these products is generally one year or less.
Vaccinating every year means vets are actually violating recommended dosage. I honestly do not understand how this is allowed and what the problem is with vets!!
Infectious core vaccines are not only highly effective, they also
provide the longest DOI, extending from 5 yr up to the life of the
dog. A[t least a] 3 yr interval is currently recommended for revaccinating
adult dogs with infectious viral core vaccines. I