This is actually a bacterial disease, so the protective "vaccination"
is actually a "bacterin". In many areas of the country, this disease is
not common and the leptospirosis portion of the vaccine combinations is
thought to be the most common cause of reactions. For this reason, many
veterinarians no longer include it in their vaccination recommendations,
IF they practice in an area in which it is not common. Your vet can tell
you whether or not it is necessary in your area.