BCG (Bacille Calmette-Guérin) vaccine, which was first introduced in France in 1908, is the only vaccine that has produced significant immunity against tuberculosis (TB) and at the same time has proved safe enough for use in humans. In the UK, BCG vaccination is usually considered for the following groups of people: (1) Infants living in areas with a high TB incidence (more than 40 cases per 100,000 people) (2) Unvaccinated children and young adults arriving from countries with a high prevalence of TB (3) Children and newborn infants in close contact with a person with TB1 (4) Health workers, such as nurses and laboratory scientists, and others likely to be exposed to infection in their work and (5) Veterinary workers who handle animals susceptible to TB. The vaccine is rarely given to those aged over 16 nor to those older than 36 (in whom it has been found to be ineffective) and cannot be used in those with untreated cancers or who are HIV positive, have a positive skin test for TB or are pregnant.

A pre-vaccination skin test, called a tuberculin test, is necessary in all persons aged over 6 years (except children regarded as high risk), and only those with negative tuberculin reactions are vaccinated. This is because those with a positive test have previously encountered the TB bacillus so are likely to be immune to infection (or, of course, they have active TB). Complications are few and far between. A local reaction at the site of vaccination usually occurs between two and six weeks after vaccination, beginning as a small papule that slowly increases in size. It may produce a small ulcer. This heals after around two months, leaving a small scar. (See IMMUNITY; TUBERCULIN.)