A shingles vaccine overdose is unlikely, since each vial of shingles vaccine contains just one dose. It is not known what to expect from an overdose with shingles vaccine.
Your healthcare provider must store the shingles vaccine in the freezer before it is mixed. After it is mixed, it should be given within 30 minutes. It is okay to keep the unmixed vaccine at refrigerator temperature for up to 72 hours (3 days) before mixing and using it. After 72 hours at refrigerator temperature, it must be discarded if not used.
Currently, there is no generic version of the shingles vaccine licensed for sale (see Generic Zostavax).