Comparison of tuberculin skin test response after three modalities of neonatal BCG vaccination

The aim of this study was to determine the tuberculin skin test (TST) response to three different BCG modalities [0.1 ml Tokyo (n = 104), 0.05 ml Pasteur-Mérieux (n = 137) and 0.1 ml Pasteur-Mérieux (n = 100)] in a cohort of healthy newborns 5 months after vaccination at birth in Santiago, Chile. Among the 341 infants, 91.2% had a response to TST, and the mean ± SD TST reaction size was significantly larger in infants receiving the Tokyo strain than in those receiving the 0.05 ml or 0.1 ml Pasteur-Mérieux strains (4.4 ± 2.0, 3.5 ± 1.3 and 3.1 ± 1.4 mm, respectively; P < 0.0001). The mean ± SD of the BCG scar size was significantly lower in infants vaccinated with the Tokyo strain than in those vaccinated with the 0.1 ml Pasteur-Mérieux strain (3.9 ± 1.2 vs. 4.3 ± 1.1 mm; P = 0.03) and no significant difference was found between infants receiving the Tokyo strain and the 0.05 ml Pasteur-Mérieux strain. However, the differences in TST size induced by diverse BCG vaccination modalities may not reflect the quality of the immunologically induced response in terms of TB protection.