TB vaccine trial provides insights into BCG Revaccination

TB vaccine

A nonprofit organization – Aeras has directed efforts towards creating vaccines against tuberculosis (TB). In a recent announcement the organization revealed results from an innovative clinical trial which said that TB vaccines prevented sustained infections among high-risk adolescents.

On basis of a phase 2 trial in South Africa, the revaccination with the Bacille Calmette-Guerin (BCG) significantly minimized the sustained TB infections among adolescents. Moreover, an experimental vaccine candidate H4:IC31 also reduced sustained infections, although not at significant levels.

Based on the report, the trend observed for H4:IC31 is a first of its kind; a subunit vaccine indicated the ability to protect humans against a TB infection or disease.

The study experiment involved the participation of 990 HIV-negative, and health adolescents aged between 12-17 years. The participants were vaccinated as infants with BCG and were randomized into three study arms, placebo, H4:IC31, or BCG revaccination. Later they were screened to ensure that they were not infected with Mycobacterium tuberculosis (Mtb) prior to vaccination in the study.

On the basis of a QuantiFERON®-TB Gold in Tube (QFT-GIT) test, TB infections were developed during the study, helped to diagnose TB infections. During the trial, individuals that were negatively tested for QFT-GIT were determined to not have a TB infection. The trial also measured the rate at which individuals were converted to QFT-GIT positive, on basis of the evidence of TB infection. Individuals tested with QFT-GIT positive over 6 months, were considered to have a sustained infection.

The results of the study were presented at the 5th Global Forum on TB Vaccines in New Delhi, India.

“We are pleased to have performed the first-known randomized, placebo-controlled prevention-of-infection trial for TB and to have demonstrated that vaccination has the potential to reduce the rate of sustained TB infection in a high-transmission setting. While neither vaccine proved to be statistically significant in preventing an initial TB infection, we are extremely encouraged by the signals observed for both vaccines in preventing sustained TB infections. We believe the results from this novel trial design will provide significant scientific benefit to the field in understanding TB infection, and based on this positive signal, we look forward to testing the potential of such vaccines to prevent TB disease among uninfected adolescents in a larger, more traditional prevention-of-disease clinical trial,” according to Mark Hatherill, MD, Director of the South African Tuberculosis Vaccine Initiative (SATVI) at the University of Cape Town.