TB NIH ImageScanning electron micrograph of Mycobacterium tuberculosis bacteria, which cause tuberculosis. Credit: National Institute of Allergy and Infectious Diseases, National Institutes of Health

Tuberculosis (TB) is an airborne disease caused by infection with Mycobacterium tuberculosis (M.tb). It is the world’s deadliest infectious disease and one of the top 10 leading causes of death overall. In 2017, an estimated 1.6 million people died as a result of TB disease.

Low- and middle-income countries account for 97 percent of reported TB cases, according to the World Health Organization (WHO). Thanks in large part to the increased availability of HIV treatment in these countries, the number of TB cases is down globally. But there were still 10 million new cases of TB disease in 2017, according to the WHO, and the emergence of drug-resistant TB is a growing global public health crisis. The only licensed TB vaccine, the bacille Calmette-Guérin (BCG) vaccine, was developed almost 100 years ago and is still widely used to prevent TB disease in infants and children. However, its efficacy is variable and there is currently no vaccine that is effective in preventing TB disease in adults, who, along with teens, are most at risk for developing and spreading TB. Development of new TB drugs and more effective vaccines remains a top priority.

Now, after decades of research, there is a renewed optimism for TB vaccines. In 2018, a Phase II trial conducted in South Africa showed that revaccinating adolescents with the same BCG vaccine they received as infants significantly reduced occurrence of sustained TB infections. Another Phase IIb efficacy study, conducted by Aeras in collaboration with GSK, showed that the GSK investigational TB vaccine candidate M72, administered along with the company’s AS01E adjuvant, protected against active pulmonary TB disease in adults, with an overall vaccine efficacy of 54 percent. These findings, if confirmed in follow-up studies, would represent a breakthrough in the quest to develop an effective TB vaccine. These trials could also provide valuable insights that scientists can use to design even better vaccine candidates.

Fast Facts about TB and HIV

TB primarily affects the lungs, though the bacteria can infect any organ. According to the WHO, almost one-quarter of the world’s population has latent TB infection and is at risk of developing active TB disease. The situation is even more dire for people living with HIV, for whom TB disease is the leading cause of death. In addition, people living with HIV:

  • Accounted for 9 percent of the cases of TB disease reported globally in 2017; 72 percent of these cases occurred in Africa.
  • Accounted for nearly 20 percent of all deaths attributed to TB in 2017.
  • Develop TB disease at a rate 20 times higher than the rest of the population.
  • Experience poorer health outcomes from TB disease, even when treated.
  • Face an increased mortality risk from multi-drug resistant TB if diagnosis is delayed.