Vaccine against tuberculosis, known as Bacille Calmette-Guerin (BCG) discovered by two French scientists, Albert Calmette and Camille Guerin in 1922, has got its own limitations, and its efficacy is highly variable. Still the vaccine is recommended for administration to all newborn to protect them against pulmonary and extrapulmonary tuberculosis.

The newborn should not be denied this vaccination. If it is ignored, and the child is faced with a serious tuberculous infection, he may suffer from the active disease, before he develops the primary complex. However, if the infection is mild, a primary complex will develop in a natural way, and the BCG vaccination will be of no value, as the child has already acquired natural resistance, of course under risk. As just mentioned, had this infection been a gross one, the newborn would have developed frank tuberculosis, leading even to death.

The BCG vaccination works on the principle that if a newborn is vaccinated (or already infected in a natural way), he will face the subsequent infection much better, and the tubercle bacilli on entering the lungs are likely to be killed. However, as already mentioned, the usefulness of this vaccine does not seem to be up to the mark.

In this vaccination, the strains of Mycobacterium bovis are weakened in their virulence (i.e. they become unable to produce the disease), and hence, when the BCG vaccination is administered, it will only cause an 'infection', and there will be no danger of the active disease.

Even if the BCG vaccination has been administered in a newborn who has immediately developed a mild infection/primary complex, for example when the child is born of a mother suffering from active tuberculosis, it will not cause any harm except that the local lesion/ ulcer at the site of injection will be more marked. Hence the BCG vaccination is usually done in the first few days following birth, and before the child contracts the disease.

In highly developed countries like the USA, this vaccine is only restricted to newborns who are more prone to tuberculosis, for example, when the baby is born of a mother suffering from the active disease, or the child is in close contact with a highly infectious drug-resistant patient of tuberculosis. In such countries, the BCG vaccination is not administered, in general, to all newborns, on the plea that this vaccine makes the tuberculin test positive. Hence this test loses its value in identifying 'infected' cases of tuberculosis, in a specific community /population, as may be required in certain circumstances.

However, the BCG vaccination has little value in the case of adults, as reported in some studies. It has also been mentioned that the vaccination may prevent the reactivation of dormant/hidden tubercle bacilli which may be lying in the body, but it may not prove helpful, when there is infection of tuberculosis from outside.

For vaccination of the newborn, 0.1 ml of the vaccine is administered intradermally in the uppermost part of the upper arm (deltoid). A crust is formed within 4 days approximately, which heals in about 4-6 weeks, and the child thus develops hypersensitivity.