VPM1002 vaccine shows 50% efficacy against extrapulmonary TB in household contacts in phase 3 trial

OBJECTIVE: To evaluate the safety and efficacy of VPM1002 and Immuvac in reducing the incidence of microbiologically confirmed tuberculosis (TB; pulmonary TB and extrapulmonary TB), development of latent TB infection, and immunogenicity. DESIGN: Phase 3 randomised clinical trial (PreVenTB trial). SETTING: 18 sites across six states of India. PARTICIPANTS: 12 717 healthy household contacts (aged ≥6 years) of patients with a smear positive TB test. INTERVENTIONS: Participants were randomly assigned in a 1:1:1 ratio (using block randomisation with variable sample size) to receive an intradermal injection of VPM1002, Immuvac, or placebo in both arms. After one month, a second dose was administered in one arm to 11 829 healthy participants. OUTCOME MEASURES: The primary outcome was efficacy against confirmed TB (pulmonary TB and extrapulmonary TB) over 38 months of follow-up. Secondary outcomes were development of latent TB infection, adverse and serious adverse events, efficacy in predefined age groups, and immunogenicity. Exploratory outcomes were efficacy when considering tuberculin skin test status, and post hoc analyses of efficacy in participants aged 6-14 and according to body mass index. RESULTS: 252 and 227 participants developed microbiologically confirmed TB in modified intention-to-treat and per protocol groups, respectively. The per protocol analysis showed 65 (1.68%), 80 (2.09%), and 82 (2.13%) participants developed TB in the VPM1002, Immuvac, and placebo groups, respectively. Of these, 12 (0.31%), 16 (0.42%), and 24 (0.62%) developed extrapulmonary TB in the VPM1002, Immuvac, and placebo groups, respectively. In the per protocol analysis, VPM1002 showed vaccine efficacy of 21.4% (95% confidence interval (CI) -8.9% to 43.2%), 19.5% (-14.6% to 43.4%), and 50.4% (0.8% to 75.2%) against all TB, pulmonary TB, and extrapulmonary TB, respectively. Immuvac showed vaccine efficacy of 33.2% (-25.9% to 64.5%) against extrapulmonary TB. VPM1002 and Immuvac showed vaccine efficacy of 64.9% (-2% to 90.1%) and 66.3% (1.9% to 90.5%) against extrapulmonary TB in participants with tuberculin skin test positivity. Both vaccines were well tolerated with mild local reactions in about a third of participants. VPM1002 and Immuvac induced specific polyfunctional CD4+ T cells. Post hoc analyses showed vaccine efficacy of 64.6% (95% CI 16.3% to 85.1%) against all forms of TB, 62.1% (3.0% to 85.2%) against pulmonary TB, and 77.6% (-3.7% to 95.2%) against extrapulmonary TB in participants aged 6-14 years in the VPM1002 group. CONCLUSIONS: Both vaccines were safe but did not show any efficacy against all forms of microbiologically confirmed TB or pulmonary TB. VPM1002 showed considerable efficacy against extrapulmonary TB. Both vaccines showed efficacy against extrapulmonary TB in participants who had a positive tuberculin skin test. TRIAL REGISTRATION: Clinical Trials Registry India CTRI/2019/01/017026.