More than 100 million doses of BCG vaccine are used each year worldwide. The role of this vaccine in the global control of tuberculosis has generated controversy for several decades and has often been underestimated. Although it has not curtailed the global epidemic, BCG immunisation in children has undoubtedly reduced childhood morbidity and mortality from tuberculosis. In the linked randomised controlled trial (doi:10.1136/bmj.a2052), Hawkridge and colleagues compare the effectiveness of intradermal versus percutaneous BCG vaccination in infants from birth to 2 years of age.1

Four high quality trials have shown that BCG is about 70-80% effective in preventing disease when given to mycobacteria naive newborns.2 Efficacy was lower in trials of older children and adults, but it now seems that such trials probably included subjects who had been exposed to mycobacteria despite having negative baseline skin tests (newer in vitro assays are more sensitive than skin tests in detecting previous infection with Mycobacterium tuberculosis or non-tuberculous mycobacteria3). Children …