The quality and efficiency of immunoprophylaxis against tuberculosis have been studied in 563 children, by estimating the vaccination BCG signs. The children who have familial contacts and have been rather fully (92.3%) and effectively inoculated with BCG vaccination and in whom skin scars, 4-7 mm in diameter, have formed are at a high risk of tuberculosis due to massive infection in the bacterial isolation foci. Inadequate immunobiological defense reactions promote the progression of endogenous infection and the development of active tuberculosis in the vast majority (67.8%) children who have unestablished and unvaccinated or ineffectively vaccinated with BCG, infected under the occult bacterial isolation conditions mainly in the families where the adults have residual pulmonary changes and hypersensitivity to tuberculin the absence of immunobiological defensive reactions is the major risk factor for active tuberculosis.