Mycobacterium tuberculosis (Mtb), the ethiological agent of tuberculosis (TB), is a leading cause of human disease and death, particularly in developing countries. In the global context, TB in intimately linked to poverty, and control of TB is ultimately a question of justice and human rights. In some areas with a high burden of TB, existing strategies for TB control are currently overwhelmed by the rising numbers of cases of TB occurring in parallel with or the HIV/AIDS pandemic. Emerging mycobacterial drug resistance is further complicating the situation. After decades of steady decline, the incidence of TB is also increasing in industralized countries, mainly as the result of outbreaks in particularly vulnerable groups.
The bacille Calmette-Guérin (BCG) vaccine has existed for 80 years and is one of the most widely used of all current vaccines, reading >80%of neonates and infants in countries where it is part of the national childhood immunization programme. BCG vaccine has a documented protective effect against meningitis and disseminated TB in children. It does not prevent primary infection and, more importantly, does not prevent reactivation of latent pulmonary infection, the principal source of bacillary spread in the community. The impact of BCG vaccination on transmission of Mtb is therefore limited.
The biological interaction between Mtb and the human host is complex and only partially understood. Recent advances in areas such as mycobacterial immunology and genomics have stimulated research on numerous new experimental vaccines, but it is unlikely that any of these urgently need vaccines will be available for routine use within the next few years. In the meantime, optimal utilization of BCG is encouraged.
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