The median PPD-specific IFNγ response on an enzyme-linked immunosorbent spot assay after intradermal BCG infection was similar to that seen in previous studies, with a broad peak from day 7 to day 14.4,5 The response was stronger after aerosol BCG infection than after intradermal infection at the day 7 peak, before decreasing to similar levels to the intradermal group at later timepoints. This evidence concerns the gene IFNG and infection.