FeedbackBCG is a live attenuated bacterial vaccine derived from Mycobacterium bovis that was originally isolated in 1902 from a tuberculous cow. BCG has demonstrated significant effectiveness, but protection has not been consistent against all forms of TB in all age groups. BCG has also shown effectiveness in preventing leprosy (caused by Mycobacterium leprae) and Buruli ulcer (caused by Mycobacterium ulcerans) (31).
BCG provides good (up to 90%) protection against severe forms of TB, including TBM and miliary TB, if given during the neonatal period. Although neonatal vaccination also provides protection against PTB in children, it mainly prevents progression to disseminated forms of TB. A systematic review found that BCG-vaccinated children exposed to people with infectious TB had 19% less TB infection than unvaccinated children (95% confidence interval (CI) 8–29%), suggesting that BCG has a modest protective effect against M. tuberculosis infection. BCG may also have nonspecific beneficial effects on all-cause mortality (31). A randomized controlled trial comparing BCG at birth versus age 6 weeks found that vaccination was protective against non-tuberculous infectious disease during the neonatal period, in addition to having TB-specific effects (32).
BCG vaccination is recommended in countries or settings with a high incidence of TB13 or leprosy and areas where Buruli ulcer occurs. A single dose should be given to all healthy neonates at birth. If BCG vaccine cannot be given at birth, it should be administered as soon as possible thereafter. Countries with a low incidence of TB or leprosy may choose to selectively vaccinate high-risk neonates. In countries where TB incidence rates are steadily declining, the epidemiology of TB should be evaluated, and switching to vaccination of people in selected risk groups may be considered (31).
Studies have not consistently shown additional benefit of repeat BCG vaccination against the development of TB or leprosy. Revaccination is not recommended even if TST or IGRA is negative. The only older age groups for whom BCG vaccination is currently recommended are unvaccinated TST-negative or IGRA-negative schoolchildren coming from or moving to high TB incidence or high TB burden settings, and other TST-negative or IGRA-negative people at risk through occupational exposure, such as HCWs working in high TB incidence settings (31).
13More than 100 TB cases per 100 000 population