Vaccine: a product that stimulates a person’s immune system to produce immunity to a specific disease
So what do you call a product that was marketed as providing immunity, but really doesn't; instead, supposedly makes the disease not nearly as bad as it could be but for the injection?
(Whatever you want to call it, it doesn't fit the definition of a vaccine.)
https://www.cdc.gov/vaccines/vac-gen/imz-basics.htm