Abstract: Objectives To observe the influence of BCG vaccination on the humoral immunity to tuberculosis bacilli.Methods The serum antibodies to PPD(PPD IgG) of 53 recruits were measured before and after BCG vaccination(12 and 24 weeks later).The OD value of them was compared between 3 measurements.Results Before BCG vaccination,there were 2 cases(3.8%) with positive PPD IgG,At the 12th week after BCG vaccination,there were 15(28.3%)positive;Followed by next 12 weeks,there were 9(17.0%)positive.The OD value of PPD IgG was higher significantly after BCG vaccination,compared with that before(P<0 001).Conclusions The increasing of PPD IgG after BCG vaccination shows that it can boost human beings humoral immunity to tuberculosis bacilli and keep that at a high level.This may interfere with the serological diagnosis of active tuberculosis among children.

Key words: Tuberculosis, BCG, PPD, IgG