Kage520

Depends on how long it's been. It was thought the series you got as a child was sufficient, but some people lose their immunity in the ensuing decades. Older people are sometimes getting another dose of their titers are low, but I don't know the process to get those levels drawn.

Everyone's dose is unique. You'd have to slowly move the dose up (without overdoing it, because edibles last awhile) to the desired effect.