A candidate vaccine against Mycobacterium tuberculosis has shown 49.7% efficacy against progression to active pulmonary TB in adults with latent disease, according to final three-year phase 2b study results published in the New England Journal of Medicine.
From August 2014 through November 2015, researchers enrolled adults between 18 to 50 years with M.tuberculosis infection without evidence of active disease at centres in Kenya, South Africa, and Zambia.
Study participants were randomly assigned in a 1:1 ratio to receive two doses of either the adjuvanted recombinant protein vaccine M72/AS01E or placebo, administered one month apart, and followed for three years after the second dose.
Among the 3,289 participants in the according-to-protocol efficacy cohort, 13 of the 1,626 participants in the M72/AS01E group, compared with 26 of the 1,663 participants in the placebo group, had active pulmonary TB that met the first case definition (incidence, 0.3 vs. 0.6 cases per 100 person-years).
When analysed using an unadjusted Cox regression model, overall vaccine efficacy at month 36 was 49.7% (95% CI, 2.1-74.2).
Serious adverse events, potential immune-mediated diseases, and deaths occurred with similar frequencies in the two groups.
The results support further evaluation of M72/AS01E through larger and longer studies conducted in a broader range of populations, the researchers concluded.