World atlas on TB vaccination launched

World Atlas on TB vaccination published Copyright: Hardin MD

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[NEW DELHI] A world atlas on tuberculosis (TB) containing detailed information on current and past vaccination policies and practices in 180 countries, could help with management of the disease, according to its developers.

Researchers from McGill University, Canada, who published an article on the ‘BCG (Bacillus Calmette-Guerin) World Atlas’ last month (22 March) in PLoS Medicine, described it as a "first-of-its-kind" searchable website for clinicians, policymakers and researchers.

The Bacillus Calmette-Guerin (BCG) vaccine, developed in 1921, is still the only vaccine against TB. It protects children against the disease, but its efficacy in adults and the elderly is controversial.

Scientists face an uphill task in their efforts to improve or replace the vaccine. Part of the problem is a lack of a precise approach or strategy, according to a review on Indian efforts by researchers from the University of Delhi, South Campus, and the Indian Institute of Science, Bangalore, due to be published in the journal Tuberculosis.

Only 10 per cent of people infected with the bacterium develop the disease, but the dormant infection surfaces whenever the immune system becomes weak, for example in HIV-infected patients.

Despite many research advances, gaps in knowledge remain. Scientists have not yet cracked how the germ evades the host immune system. There are no ‘markers’ or molecules that can serve as indicators of whether a vaccine works or not, no suitable animal models to test the vaccine, and no sensitive and specific diagnostic tools.

And, even after 85 years of use, scientists still do not know why the BCG vaccine works with some populations but not others.

But, the review, said, several advances "augur well" for a more effective TB vaccine. These include the identification of defects in the pathways of some immune molecules, and the contribution of newer immune molecules.

Several Indian research teams are attempting to find and test new ‘antigens’ or protective proteins in the Mycobacterium tuberculosis bacterium, or related ones such as M. bovis, M. fortuitum, and M. habana; while others are working on vaccination strategies.

Madhukar Pai, an assistant professor at the department of epidemiology and biostatistics at McGill University, who was part of the team that developed the atlas, told SciDev.Net  that one of the biggest challenges in TB vaccine development is the long, time-consuming and expensive clinical trials. 

"So, while millions of dollars are being invested in new TB vaccines, it will be a while before we see results," Pai said.