This study consists of a follow-up of 1165 adolescent children of whom 601 had been vaccinated with BCG during infancy. The remainder, 564, had been followed from infancy as controls.Approximately 550 of these cases received roentgenographic examinations which were compared with RGs taken during the first 5 years of life.As was to have been expected, roentgenographic evidence of healed lesions of primary pulmonary tuberculosis was found much more frequently in the control group than those in the group vaccinated by BCG.Of the 298 vaccinated cases which received RGs there were three with evidence of a healed pulmonary primary complex. There were also two cases with re-infection tuberculosis of the lungs. Of the 286 controls, there were 27 showing evidence of healed pulmonary primary complex. There were no cases of re-infection tuberculosis in the control group.A study of the three vaccinated cases which developed evidence of a healed primary pulmonary complex suggests that in two of the cases the BCG vaccine was weak or inadequate while in the third case the child has been exposed and was probably vaccinated in the pre-allergic phase of a human tuberculosis infection. Of the two vaccinated cases that developed signs of a re-infection tuberculosis in adolescence, it is evident in the first case that the allergy following a weak BCG inoculation subsided and the child received a subsequent exposure to open tuberculosis, later with the development of the re-infection tuberculosis. The second case with re-infection tuberculosis showed evidence of having lost the tuberculin allergy approximately three years after inoculation.As yet no evidence is forthcoming on the ability of BCG vaccine given in infancy to diminish the tuberculosis mortality rate among adolescents and young adults. There were no tuberculosis deaths in either group.It is evident that the BCG inoculation has the ability to prevent a pulmonary primary tuberculosis, at least during the period of postvaccination tuberculin allergy.There is no evidence to indicate that BCG given in infancy is capable of preventing reinfection tuberculosis in adolescence. It is yet to be demonstrated that if the post-BCG tuberculin allergy is maintained the re-infection type of tuberculosis will be avoided.It would appear from this study that there is great difficulty in determining the efficacy of BCG unless some method of maintaining the potency be devised and a standard accurate means of inoculation be used.It is suggested by this study that the BCG tuberculin sensitivity be maintained by revaccination whenever the skin reaction becomes negative.
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