[kjc]

Originally Posted by 107barney

My understanding is that the older lepto vaccine only protected against two serovars (strains) of leptospirosis that were commonly seen in ill dogs when the disease was first a problem. The new vaccine however covers 4 serovars and these cover some illnesses seen more recently in dogs.
Canine leptospirosis: A re-emerging disease in the United States (Proceedings) - Veterinary Healthcare

Great post... but her dog has been vaccinated with the 'old' Lepto vaccine.