The Prevention of Tuberculosis

With regard to tuberculous infection we may divide the life of a human being into three periods: 1. The pre-infection period; 2. the incubation period; and 3. the period of latency and of manifest tuberculous disease. The end of the pre-infection period is determined by the occurrence of. the first infection. The end of the incubation period is marked by the establishment of tuberculin sensitivity. The prophylactic measures vary during these three periods. The pre-infection period is the period of choice of specific vaccination. An already infected child has acquired by natural virulent infection a degree of specific immunity that is far stronger than the artificial immunity which is acquired by vaccination. Vaccination cannot prevent tuberculosis infection, but it diminishes the risk of virulent disease after the first infection, and may, therefore, be called specific disposition prophylaxis. During the same period tuberculosis is prevented by protecting the child against infection. This we call infection prophylaxis. There is reason to believe that the period of infection prophylaxis may with benefit be extended even to the incubation period. It may be of prophylactic value to prevent new exogenous infections during this pre-immune period. The value of adopting special measures subsequently in order to prevent the common exogenous rein -fections in allergic subjects is, according to my experience and opinion, questionable. For my part, I have never seen a case of clinical tuberculosis the manifestation of which could be traced to a new exogenous infection. On the other hand, I have followed-up thousands of tuberculin-positive children exposed to exogenous re-infections without being able to note any bad effect on the chil-dren's health. During the third period, after the tuberculin sensitivity has been established, we try to prevent the manifestation of tuberculous disease by strengthening the natural resistance and general health of those infected. This is the period of non-specific disposition prophylaxis. This form of prophylaxis need not be confined to those who are tuberculin-positive. It may be extended even to uninfected sub