In Lübeck, Germany, children were orally vaccinated with BCG at birth.   In the first few months of 1930, a laboratory error led to a catastrophe in that a virulent strain of M. tuberculosis was mixed with M. bovis BCG.  A total of 72 of the 251 children affected died in the disaster.  About 100 children were repeatedly tested with tuberculin and the interval between infection and conversion was thus determined.  The median interval between infection and conversion was 55 days with the above distribution.  The actual interval is shorter, because tuberculin tests could obviously not be done on a daily basis.

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