Does BCG vaccination protect against infection with ?

Protection against infection by the bacille Calmette-Guérin vaccine against remains a subject of controversy. We investigated the association between BCG vaccination at birth and infection by . This was a secondary analysis of data from tuberculin skin test (TST) surveys in Vietnamese schoolchildren between 1988 and 2001. We investigated whether a BCG scar was associated with a lower prevalence of TST positivity, adjusting for BCG-induced variation by varying cut-off values for a positive TST. We found a positive association between BCG scar and TST positivity. The strength of the association decreased with increasing TST cut-off values; however, it never inverted significantly, irrespective of geographic region and survey year. In Vietnam, BCG vaccination was not associated with reduced infection prevalence as measured using TST. This in contrary to a similar study conducted in Tanzania. These contradictory findings may be explained by geographical differences and the relatively high prevalence in Vietnam of the Beijing genotype, which is reported to be capable of circumventing BCG-induced immunity.