EVALUATION OF TUBERCULIN REACTIVITY IN BCG-IMMUNIZED SIBLINGS

The purpose of the present study was to determine in BCG-immunized sib ships less than or equal to 14 yr of age whether the correlations of i ntensity of tuberculin reactivity support a genetic regulation of the response to BCG immunization. The study population consisted of 659 he althy children living in 265 households exposed to an adult with tuber culosis: 38 children did not have a BCG: scar, 327 children had one BC G scar, and 294 had two BCG scars from vaccinations at birth and at 6 yr of age. There were 603 full siblings, 16 half-siblings, and 40 unre lated children. Tuberculin testing was performed by one trained nurse. Sibling correlations of the intensity of the tuberculin response were calculated after adjusting for various nongenetic covariates that cou ld be important in predicting it. The sibling correlations were signif icant at the 1% significance level. There was no significant correlati on of tuberculin reactivity among unrelated children in the same house hold. These results are consistent with genetic regulation of the deve lopment and persistence of tuberculin reactivity after BCG immunizatio n.