Accelerated Bacille Calmette-Guérin reactions: More than meets the eye

An accelerated local injection site reaction following Bacille Calmette-Guérin (BCG) vaccination has been associated with underlying active tuberculosis (TB) in high TB-prevalence settings. The clinical significance of this accelerated BCG reaction in individuals without TB symptoms, particularly in low TB-prevalence countries, is unclear.Using safety surveillance data and baseline interferon-gamma release assays (IGRA) within an international randomised trial of BCG vaccination in healthcare workers (the BRACE trial), we aimed to determine the incidence, and investigate for clinical implications, of an accelerated BCG reaction in asymptomatic adults in low and high TB-prevalence settings.An accelerated BCG reaction occurred in 755/1984 (38 %) of BCG-vaccinees. Although more frequently painful, tender, erythematous and/or swollen within the first fourteen days of vaccination, compared with non-accelerated reactions, the majority of injection site reactions were mild and did not meet criteria for an adverse event.Prior mycobacterial exposure, through prior BCG vaccination (OR 2.46, 95%CI 1.93–3.13, p