Evaluation of cell-mediated immune responses to two BCG vaccination regimes in young children in South Korea

Children in South Korea are vaccinated with either BCG Pasteur vaccine intradermally (ID), or with BCG Tokyo vaccine given by multipuncture device (MP). Data from a recent national survey indicated that in children under 6 years old, 31.1% had received the ID vaccine and 64.5% the MP vaccine. To compare the T cell responses induced by the two vaccines, children aged 3-7 were recruited and tested for tuberculin skin test reactivity and for in vitro IFN-γ responses to mycobacterial antigens. DTH responses were not significantly different in children vaccinated by either the ID or MP vaccines. PPD-induced IFN-γ was measured in supernatants of 6-day diluted whole blood cultures. IFN-γ production to PPD was not significantly different in the two vaccine groups, although there is a trend that the MP group gives a higher proportion of IFN-γ positivity than the ID group. In addition, when IFN-γ responses to the antigens ESAT-6 and CFP-10 were assessed in the 6-7 year old group, there was no significant difference between the two vaccine groups. Thus, there was no evidence that the increasing use of MP vaccination has reduced protection against M. tuberculosis in young children in South Korea, based on immunogenicity as assessed by DTH and IFN-γ responses to PPD, and also equivalent frequency of responses to ESAT-6 and CFP-10.