Vaccines against tuberculosis: moving forward with new concepts.

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), infects one-third of the world’s population. While most infected individuals develop latent TB, 5–10% of infected individuals develop active TB. In addition, although most infected people with latent TB remain asymptomatic, they have approximately 10% lifetime risk of developing into active TB. This results in approximately 8.8 million new cases of TB per year and 1.4 million deaths per year worldwide due to TB [1]. In addition, antibiotic treatment regimes for TB treatment are long and therapeutic strategies such as directly observed drug therapy require significant infrastructure. The recent emergence of multidrug-resistant bacteria along with increased incidence of HIV-associated TB further emphasizes the need for better vaccines against TB [1]. Mycobacterium bovis BCG is the only available vaccine for TB; however, the protective efficacy is variable and ranges from 0–80% in different geographical locations [2]. This review will briefly discuss possible reasons for failure of licensed TB vaccines, overview of TB vaccines in clinical trials and discuss new immune protective correlates that may provide some insights into future design of TB vaccines.