Limited efficacy: New TB vaccines safe but protection limited, says study

The two new tuberculosis (TB) vaccines - VPM1002 and Immuvac – are safe for use in adults and children in India but may not protect against all forms of the infectious disease, according to phase-3 trial results published in The British Medical Journal.

Phase-3 trials are large-scale, randomised clinical studies that evaluate the safety and effectiveness of a new intervention by comparing it with a standard treatment or placebo.

Researchers, including those from the Indian Council of Medical Research (ICMR), conducted the PreVenTB trial to assess the safety and efficacy of the two vaccines in reducing TB incidence.

India currently administers the Bacillus Calmette-Guérin (BCG) vaccine at birth. The vaccine protects infants against severe forms of TB but offers limited protection in adolescents and adults.

VPM1002 is a recombinant BCG vaccine developed by Serum Life Science Europe GmbH, while Immuvac is an inactivated vaccine developed by ICMR and Cadila Pharmaceuticals.

The study included over 12,700 household contacts of TB patients across 18 sites in six states and Union territories, including Delhi, Maharashtra and Tamil Nadu. Researchers randomly assigned participants to receive VPM1002, Immuvac, or a placebo and followed them for 38 months.

Researchers found that both vaccines were safe and generated an immune response. However, they did not demonstrate significant efficacy against all forms of micro-biologically confirmed TB or pulmonary TB.

The study also found that while neither vaccine provided broad protection or prevented latent TB infection, both reduced progression from latent infection to active TB in some cases.

VPM1002 showed about 50.4% effectiveness against extrapulmonary TB across all age groups. Researchers said this finding could offer meaningful public health benefits, as extrapulmonary TB often carries a higher risk of mortality.

In children, VPM1002 protected against all forms of TB in the six to under-14 age group, while Immuvac provided limited protection against extrapulmonary TB in children aged six to under-10.

However, neither vaccine protected underweight children or adults, suggesting that nutritional support may need to accompany vaccination, the researchers noted.

Press Trust of India