BOOSTER EFFECT OF TUBERCULIN TESTING IN HEALTHY 6-YEAR-OLD SCHOOL-CHILDREN VACCINATED WITH BACILLUS-CALMETTE-GUERIN AT BIRTH IN SANTIAGO, CHILE

Abstract

In order to determine whether tuberculin testing caused a booster effect in children vaccinated with Bacillus Calmette-Guerin (BCG) at birth, we studied forty 6-year-olds by repeat tuberculin testing 2 weeks later on the contralateral forearm. All children were healthy and had no known exposure to tuberculosis. None of the children had a history of mycobacteriosis other than tuberculosis. The mean induration was 2.3 .+-. 1.8 mm for the first tuberculin reaction and 7.6 .+-. 3.3 mm for the second tuberculin reaction (P < 0.005). Four children had positive reactions (.gtoreq. 10 mm) to the first purified protein derivative test; 18 children were positive upon retesting. Eleven of these latter children had increases of at least 6 mm from reactions < 10 mm to .gtoreq. 10 mm. The size of the BCG scar was significantly correlated to the size of both the first and second purified protein derivative reactions (P < 0.01), suggesting that the increased reactivity upon retesting was a consequence of sensitization induced by BCG vaccination 6 years earlier. All children remained healthy after this study was completed. Retesting of tuberculin reactivity within 2 weeks in BCG-vaccinated children with reactions < 10 mm will produce reactions .gtoreq. 10 mm in some healthy children who may not require antituberculosis treatment.