Bacillus Calmette–Guérin (BCG) vaccine contains a live attenuated strain of Mycobacterium bovis, which provides 64% efficacy against tuberculous meningitis and 78% efficacy against disseminated tuberculosis.1 A number of local adverse reactions are recognised (abscess, suppurative lymphadentitis, keloid formation). An increased number of local complications were reported in the UK and Ireland since the introduction of a new BCG strain in 2002.2 ,3 It is important to distinguish between a normal vaccine response, a local complication and the very rare cases of systemic BCG infection that occur with immunodeficiency. Antibiotics and/or anti-tuberculous medication are rarely needed, except for systemic BCG infection.

Natural history of BCG site

After intradermal injection, BCG multiplies at the inoculation site, then spreads to regional nodes. A normal reaction is a red indurated area, which progresses to a local lesion that may ulcerate 2–3 weeks after vaccination. A crust is formed around this induration for 3–4 weeks. At 6–10 weeks, the crust falls off, leaving a flat 3 to 7 mm scar. Regional lymphadenopathy <1 cm (95% in the axilla) is considered a normal reaction to the vaccine.4 This ‘simple’ lymphadenitis occurs 63 days (range 16–87) after BCG vaccination5 and resolves spontaneously by 9 months.6 Lymphadenitis may be more common when BCG is given to infants <6 months old compared with older children and adults.5

Complications of BCG

Local complications occur in one in a thousand people given BCG vaccine.3 ,7