Abstract

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. © 2006 Royal Society of Tropical Medicine and Hygiene.