Tuberculin reaction, BCG scar, and lower female mortality.

BACKGROUND

Recent studies have suggested that bacille Calmette-Guérin (BCG) immunization may have a nonspecific beneficial effect on infant survival and that the effect may be more pronounced among girls. In a prospective birth cohort, we examine whether a positive tuberculin skin test and BCG scar in response to BCG immunization were related to better overall survival in Guinea-Bissau and, if so, whether the effect was sex-specific.

METHODS

Skin tests and BCG scarring were monitored at ages 2 months (n = 2332) and 6 months (n = 1817) in children born from March 2000 to July 2002. A tuberculosis (TB) surveillance system allowed us to exclude from the analysis children with likely TB exposure. The children were followed for survival until 18 months of age.

RESULTS

Among children with a tuberculin skin test at 2 and 6 months of age, the mortality rate ratio for skin test reactors (>1 mm) versus nonreactors (0-1 mm) was 0.54 (95% confidence interval = 0.30-0.99). Comparing children with and without a BCG scar, the ratio was 0.55 (0.31-0.96). The effect of a skin test reaction or a BCG scar seemed stronger among girls; for those with positive reaction, the mortality ratio was 0.31 (0.11-0.88) among girls and 0.84 (0.39-1.82) among boys; and for BCG scar, the results were 0.41 (0.21-0.82) and 0.88 (0.34-2.30), respectively.

CONCLUSIONS

A good response to BCG vaccination is related to lower child mortality. The effect seems most pronounced among girls. The findings may have implications for future vaccine trials and policy.