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TB vaccination called BCG is not indicated for everyone. Infants are given this vaccination as part of immunization schedule.
It is not 100% effective. Rather only about 50% of individuals who recieved vaccination are protected and almost 80% are still suceptibe to infection but with weaker response.
Its peak effect may stay in body for upto almost 10 years even though antibodies stay in blood lifelong to some extent.
If someone is at risk of acquiring TB, then TB prophylaxis with certain meds like Isoniazid alongwith pyridoxine is gven.
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Repeat dose is not recommended routinely. Only certain healthcare workers may get it who are at risk of acquiring TB infection by bacteria that is resistant to rifampin etc.
Otherwise for normal healthy individuals, it is not recommended.