Waning of postvaccination tuberculin hypersensitivity and its restoration by tuberculin testing

Postvaccination tuberculin reactions among infants and primary school entrants were observed in an area where BCG vaccination with multipuncture method had been given, practically only once in early childhood, and where postvaccination tuberculin testing had been repeated rather arbitrarily at varying intervals. The findings confirm the phenomenon long known as "boosting" or the "restorative effect" of the postvaccination tuberculin testing to the tuberculin hypersensitivity caused by BCG vaccination. It may have serious implications on the current revaccination scheme of Japan and also on the interpretation of the results of repeated tests for mass examination as well as individual contact examination which has become an established routine in the tuberculosis service.