HomeThe efficacy of BCG has been debated for many years, even though more than 3 billion doses of the vaccine have been administered. One systematic review estimated that there is a protective efficacy of 19% against infection after exposure, and 58% protection against progression to disease, among BCG vaccinated children compared with unvaccinated.142 In a second review, the protection against meningeal and miliary TB for infants and young children was estimated to be 85-92%, and the protection against pulmonary disease in children was 74%.143 The efficacy of BCG in adults is uncertain but is thought to be lower than in children. The duration of the protective effect of BCG against pulmonary and extra-pulmonary TB is at least 10 years, with evidence that longer-term efficacy declines with time.144 There is good evidence from randomized trials that revaccination does not confer added protection.145,146 There is also evidence that TST reactions do not correlate with protective immunity.147,148
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