Background

Modelling suggests that the most effective contribution to TB control would be a vaccine that prevents pulmonary TB in adolescents and young adults.

Currently, Bacille Calmette-Guérin, known as BCG, is the only licensed TB vaccine. However, it does not offer substantial protection against pulmonary TB in Mtb–infected adults. Therefore, BCG has a limited impact on the transmission of Mtb in adults.

TB treatment is lengthy, and compliance is often incomplete, resulting in an increased incidence of multi-drug resistant (MDR)- and extensively drug-resistant (XDR)-TB. Thus, an effective TB vaccine to prevent TB disease is critical for ending the TB epidemic.

Several vaccine candidates are under investigation. Accurate, relevant site-specific epidemiology data to support site selection will enable robust trial size and duration calculations for the Phase 3 vaccine efficacy trial. This study will aid in refining the sample size, duration and building capacity to conduct the planned vaccine efficacy study that will follow.

Objectives

Primary

• To describe the proportion of IGRA positivity by site;
• IGRA status (positive/negative/indeterminate) at screening.

Secondary

• To assess the association of age with the proportion of IGRA positivity by site;
• To describe the overall incidence of suspected and laboratory-confirmed pulmonary TB (disease);
• IGRA status (positive/negative/indeterminate) at screening;
• Suspected pulmonary TB during the study follow-up period;
• Laboratory-confirmed pulmonary TB during the study follow-up period.

Exploratory

• To describe changes in the proportion of IGRA positivity by site;
• To describe the association between IGRA interferon-gamma (IFN-gamma) concentration at screening and progression to pulmonary TB.