Step to improve TB vaccine

In what may one day lead to an improved BCG vaccine against TB, an Indo-US team has come out with a novel strategy to improve the efficacy of the popular TB vaccine, which is given to children as a part of the universal immunisation programme.

Even though the new strategy has not yet been put under the rigours of a clinical trial, the scientists are hopeful because of encouraging animal trial results, which clearly show that the new strategy improves the BCG vaccine's efficacy by almost 100 per cent.
Nearly one-third of global population – 1.86 billion people – are infected with tuberculosis, which kills close to 50,000 people daily.

The disease is spreading fast because of HIV and fast growth of drug-resistant tuberculosis. Modelling studies demonstrated that even a modestly effective vaccine (50-70 per cent efficacy) in combination with drug therapies could save tens of millions of lives and a highly effective vaccine would eventually control the disease.

The BCG vaccine, which is in use since 1921, has poor efficacy and hardly protects the adults from TB that afflicts the lungs. Even though it has some protective cover against children for bone TB and meningitis, BCG injection does not protect adults from lung infection. The efficacy remains poor even if the vaccine is administered as aerosol.

“We have modified the BCG vaccine with a protein called ESAT-6. The recombinant BCG was tested in animals and found to be 1000 times better than BCG given via the aerosol route,” Gobardhan Das, a TB scientist at the International Centre for Genetic Engineering and Biotechnology here told Deccan Herald.

Technical details of the findings have been published last week in the open access journal Public Library of Science Pathogen.

Globally, there are at least three other recombinant BCG vaccines developed by US and European researchers, which are in clinical trials and many more are at the research stage.

“BCG produced more controversy than protection against TB. We need a vaccine, which does what BCG fails to do for reasons we don't know. The new vaccine should protect consistently against adult TB,” said Anil Tyagi, a Delhi University professor and a veteran in TB research, who is not connected to the ICGEB study.

Tyagi pointed out that it would be extremely challenging to come out with a more efficacious BCG simply because it works extremely well in animal models.