Summary

Summary After revaccination, reactions occur at the site of injection which are morphologically similar to reactions after primary vaccination, but they regularly appear with reduced incubation period and more rapidly developing necrotic reactions parallel to the number of the vaccinations. The phenomepon persists even when the interval between the vaccinations is of several years. Further revaccination often leads to focal reaction‐ reactivation‐at the site of the first vaccination, and the tuberculin allergy may develope much more rapidly than other‐ wise, 6–18 days after revaccination. It is probable that this reaction type ‐the depth reaction‐is determined by the tuberculo‐protein in the BCG. It is found that exactly the same reaction type occurs when killed BCG are employed, either alone or alternating with live bacilli. In 2 cases tuberculin allergy was obtained after primary vaccination with killed bacilli. In infected individuals the accelerated reaction occurs on primary injection of BCG, both with live and killed vaccine. The mechanism of the depth reaction can be transmitted via the placenta.