I'm not sure of free either but I know spca and front street shelter both offer low cost shots and spay neuter.
Try Banfield pet hospital in Sacramento. They're vaccine isn't free, but I believe their initial pet exam and consultation is. They'll let you know.
The only free vaccines i am aware of is a free clinic for seniors with pets once a month. There are a few low cost vaccine clinics given by the various Sspcas in the area.
At present, I'm not aware of free vaccines. Bradshaw shelter runs a vaccine and vet clinic on Tuesday and Thursday for low income and sliding scale cost.
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