Welcome! My name isXXXXX am a 2003 graduate from UC Davis, and currently a Medical Director of a veterinary hospital.
I am sorry to hear about this concern for Max.
No, I have never heard of a pet developing lepto as a result of the inoculation.
Here is some very detailed information about lepto vaccines:Lepto Vaccines
But, because of how they are created, a lepto vaccine would not induce lepto infection.
The vaccine is well known to sometimes cause allergic reaction and illness, but not actual infection.
I hope that information has been helpful.
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