A vaccine against Mycobacterium tuberculosis has produced good results in a phase 2b trial in people with latent tuberculosis infection (TB), who represent a potential reservoir of active cases. The M72/AS01E vaccine, developed by GlaxoSmithKline in partnership with the International AIDS Vaccine Initiative, provided 50% protection against progression to active pulmonary TB during 3 years after vaccination. This level of protection is in line with World Health Organization (WHO) recommendations for new TB vaccines and an improvement on previous attempts. An earlier, two-year readout of the trial, which yielded 54% efficacy, prompted the WHO to call it “unprecedented in decades of TB vaccine research”.

The M72/AS01E vaccine is made up of an immunogenic M72 recombinant fusion protein derived from two M. tuberculosis antigens, Mtb32A and Mtb39A, with GSK’s proprietary adjuvant AS01E. The trial tested the vaccine on adults with a latent M. tuberculosis infection who were otherwise healthy. Overall, 3,575 HIV-negative participants from Kenya, South Africa and Zambia were enrolled. Of the 1,626 participants who received two doses of vaccine, 13 developed active pulmonary TB, as compared with 26 (out of 1,663 participants) in the placebo group.

A vaccine against adult pulmonary TB would be a crucial tool to halt the spread of TB. The only licensed TB vaccine, BCG (bacillus Calmette–Guérin), doesn’t reliably protect against the most common form of the disease, adult pulmonary TB. Other past attempts in various patient populations have also failed to make it over the 50% protection barrier: 31% efficacy with Sanofi Pasteur’s adjuvanted protein subunit vaccine H4:IC3; 17% efficacy with the viral-vectored vaccine MVA85A, developed by Aeras, Wellcome Trust and Oxford-Emergent Tuberculosis Consortium; 39% efficacy with Dartmouth Medical School’s cell-derived M. vaccae vaccine, and 45% protection with BCG vaccine revaccination.