Do new TB vaccines have a place in the Expanded Program on Immunization?

Several new TB vaccines are currently undergoing clinical trials. Among the most promising is a vaccine based upon the modified vaccinia virus Ankara-expressing mycobacterial antigen 85A (MVA85A). Given the widespread use of the current TB vaccine, BCG, many of the new TB vaccines are being tested for their ability to boost BCG-induced immunity. The introduction of a new TB vaccine into routine use would be facilitated by its coadministration with other vaccines as a part of the WHO's Expanded Program on Immunization (EPI). In the article under review the authors tested the immunogenicity of MVA85A given alone or in combination with EPI vaccines to infants in The Gambia. Antigen 85A-specific production of IFN-γ by peripheral blood cells was reduced significantly in infants coimmunized with EPI vaccines compared with infants who received the MVA85A vaccine alone. This study highlights a potentially important issue, which should be addressed prior to the introduction of new TB vaccines and, perhaps, other vaccines that require the induction of a so-called Type 1 T-cell-mediated immune response.