Caused by the rod-shaped bacterium Mycobacterium tuberculosis and transmitted by airborne droplets from a diseased individual, tuberculosis (TB) is a chronic infectious disease of humans (and other animals) that destroys body tissue. When M. tuberculosis primarily attacks the lungs, the result is pulmonary TB. Although effective therapy and methods of control and prevention of TB have been developed, this disease remains a major cause of mortality and morbidity throughout the world. Typically, TB kills more than 1.5 million individuals annually and is particularly problematic in Africa, Asia, and Latin America. The bacillus Calmette-Guérin (BCG) vaccine, developed for human use in 1921 and used in many parts of the world (but only rarely in the United States), protects most children from the disease. However, the vaccine is only minimally effective in adults, and is especially ineffective in adults who have already contracted the dormant form of TB. Thus, scientists have been actively seeking a vaccine that could provide protection for a greater range of the population. See also: Bacteria; Infectious disease; Lung; Mycobacterial diseases; Tuberculosis; Vaccination
One new candidate to fight pulmonary TB is the M72/AS01E vaccine. After three years of trials in more than 3500 adult human subjects in Kenya, South Africa, and Zambia, the results are very promising. Approximately 50% of the individuals receiving this experimental vaccine acquired long-term protection against TB, and no negative side effects have been reported with the use of this vaccine. Although a 50% efficacy rate is relatively low in comparison to efficacy rates of vaccines used to protect against other illnesses, the M72/AS01E vaccine still has the potential to save millions of lives. The vaccine also has been shown to prevent the M. tuberculosis bacterium from causing disease in individuals who are already infected with TB, but do not display any symptoms. Researchers are confident that the M72/AS01E vaccine could ultimately replace the old BCG vaccine for TB treatment and prevention. See also: Africa; Clinical microbiology; Medical bacteriology
Research involving the candidate vaccine is entering final trial phases. If the vaccine continues to provide favorable results in protecting individuals from TB, it could be a significant tool in the eventual eradication of this disease. In addition, the vaccine might reduce incidences of troublesome drug-resistant forms of TB because the vaccine would theoretically reduce its transmission and prevent the need for antibiotics. However, scientists estimate that another 7 to 10 years of research work will be necessary before the M72/AS01E vaccine can be approved and licensed for use. These additional investigations will need to include larger cohorts of individuals and populations located outside sub-Saharan Africa. See also: Antibiotic; Antibiotic resistance; Drug-resistant tuberculosis on the rise; Public health
