BCG (Bacillus Calmette-Guérin) is a living attenuated strain of Mycobacterium boviswhich stimulates cell-mediated immunity by producing a localised and self-limiting infection. The vaccine is given intradermally, normally in the arm, but in parts of northern Europe often in the thigh or buttock (an important consideration if looking for a scar to prove previous vaccination). Vaccination should be given around the site of the insertion of the deltoid muscle, slightly posteriorly (Fig.1). This minimises keloid scar formation and also ensures that the lymphatic drainage of the site is to the axilla, rather than to the neck glands. The cosmetic effects of persistent lymphadenopathy or scars from suppurating lymph nodes are thus minimised. Normally one to three weeks after vaccination a small red papule appears. This usually vesicates and a scab forms. The site should be kept clean and dry and exposed to air as much as possible. It can be washed with clean warm water, but should be dabbed dry and kept open. Antiseptics, creams and other local applications should not be used. Normally the vaccination site heals leaving a small, depressed scar over a three to four month period. The duration of immunity is thought to be 10-15 years, but usually patients are not revaccinated.

Indications for BCG
BCG should be used in the following circumstances:
- newborn Aboriginal and Torres Strait Islander babies in areas where tuberculosis is prevalent
- neonates and children who are likely to travel to or live in countries where tuberculosis is common
- newborn babies, if either parent has leprosy
- children and adults who have been in contact with tuberculosis and remain Mantoux negative three months after last contact.
BCG may also be considered in the following circumstances:
- healthcare workers in frequent contact with patients with tuberculosis, especially multi-drug resistant tuberculosis
- adults who will spend prolonged periods in countries where tuberculosis is common
- newborn babies living in households where they may be exposed to migrants or visitors from overseas countries with high tuberculosis rates
- children under 16 years who are in contact with a patient with tuberculosis where the infection is resistant to treatment or where the child cannot take prophylactic antituberculosis treatment.
Healthcare workers
Healthcare workers represent a special group and there are two quite different views on how they should be managed with respect to potential tuberculous infection. The American view is that BCG should not be given and that healthcare workers should be monitored with regular Mantoux tests to detect tuberculous infection which can then be treated appropriately. This is expensive and labour intensive.
In parts of Australia where exposure to environmental mycobacteria is high and where many healthcare workers have had prior BCG, Mantoux tests may prove difficult to interpret. The alternative view, that new staff should be screened by Mantoux testing and then offered BCG vaccination if the result is negative, has become less popular and has been abandoned in some states which have adopted the American policy. Nevertheless, this approach is a viable option for staff likely to be exposed to tuberculosis regularly and certainly for those exposed to multi-drug resistant tuberculosis, although this is still uncommon in Australia.