In 2012, the WHO named India the worst performer among developing nations, with 17% of the global population carrying 26% of the global TB burden. Even today, TB cases are increasing due to ineffectiveness of BCG vaccine, say experts
As one of the highest tuberculosis (TB)-burden countries, India has been on the mass immunisation drive, using Bacillus Calmette–Guérin (BCG) vaccine since 1948. A national TB control project was launched in 1962 across the country. However, according to experts, inadequate diagnosis and ineffective BCG vaccine are leading to increase in number of TB cases across the world!
According to a report from New Indian Express, Shekhar C Mande, Director of Pune-based National Centre for Cell Science (NCCS), while speaking at the Science Academies’ lecture workshop in Visakhapatnam last week said, mycobacterium tuberculosis was a serious health concern around the world because there was no new drug launched in the last three decades. If the TB patients were not treated they would infect 15 other people per annum, he added.
No wonder, in 2012, when the country completed 50 years of its TB control initiative, the World Health Organization (WHO) named India the worst performer among developing nations, with 17% of the global population carrying 26% of the global TB burden.
The most controversial aspect of BCG is the variable efficacy found in different clinical trials, which appears to depend on geography. Trials conducted in the UK have consistently shown a protective effect of 60 to 80%, but those conducted elsewhere have shown no protective effect, and efficacy appears to fall the closer one gets to the equator, say reports published in JAMA and Lancet.
According to a paper published in the Lancet in November 1995
, besides being the world's most widely used vaccine, and being directed against the world's leading cause of infectious disease mortality, BCG was the most controversial vaccine in current use. Prof PEM Fine, from London School of Hygiene and Tropical Medicine, who wrote the paper, says, "Estimates of protection imparted by BCG against pulmonary tuberculosis vary from nil to 80%. This variability has been attributed to strain variation in BCG preparations, to genetic or nutritional differences between populations, and to environmental influences such as sunlight exposure, poor cold-chain maintenance, or exposure to environmental mycobacterial infections. Evidence accumulated to date indicates that regional differences in environmental mycobacteria are responsible for much of the variation observed between populations in the efficacy of BCG against pulmonary tuberculosis."
Mr Mande from NCCS too seems to agree with the studies and research papers that are published in well-known medical journals. He told the newspaper that, "We have been trying to understand how M tuberculosis adapts itself to different conditions because it adapts itself to various environmental conditions, including different oxygen levels. My research team is finding new methods to determine structures of proteins involved in these processes and the results may help to handle the disease in a better way”.
Even the 15-year follow up trial of BCG vaccines in Chengalpattu district in Tamil Nadu by Chennai-based Indian Tuberculosis Research Centre, concluded that BCG offered no overall protection in adults and a low level of overall protection (27%; 95% C.I. -8 to 50%) in children. "This lack of protection could not be explained by methodological flaws, or the influence of prior sensitisation by non specific sensitivity, or because most of the cases arose as a result of exogenous re-infection. The findings at 15 years show that in this population with high infection rates and high nonspecific sensitivity, BCG did not offer any protection against adult forms of bacillary pulmonary tuberculosis," the study said. The results were published in Indian Journal of Medical Research, confirmed that the TB control project had lost the tool of primary prevention.
A number of possible reasons for the variable efficacy of BCG vaccine in different countries have been proposed. None have been proven, some have been disproved, and none can explain the lack of efficacy in both low-TB burden countries like the US and high-TB burden countries like India. According to a document from WHO, genetic variations in BCG strains and populations, interference by nontuberculous mycobacteria and concurrent parasitic infection and exposure to ultraviolet light are the factors that needs to be looked into while deciding effectiveness of BCG vaccines.
Even the ambitious, directly observed treatment, short course (DOTS) programme launched by the Indian government was able to save lives but not control TB. This was confirmed by the WHO in its 2012 Annual Report on TB. It is time for redesign of TB control, with alternative tactics to prevent infection and treat infection, before it caused disease?