Can BCG booster dose reduce India’s tuberculosis burden? Top TB research institute plans to find out

A child being examined for signs of tuberculosis in Faridabad, Haryana. (Image: JP Davidson via Wikimedia Commons 2.0)

The country’s apex tuberculosis (TB) research institute has planned a study to assess whether a booster dose of the Bacille Calmette Guerin (BCG) vaccine can reduce the burden of TB, a highly infectious disease that primarily affects the lungs.

The study by the National Institute of Research in Tuberculosis (NIRT), which will see the enrolment of 8,000 household contacts of TB patients, aged 6-18 years, is now seeking funding support from the department of health research under the Union health ministry.

As of now, BCG vaccination is offered to all babies at birth as part of the country’s Universal Immunisation Programme.

It is one of the most used vaccines globally to reduce the risks of natural tuberculous infection and the efficacy of BCG vaccination in newborns is well established due to its protective effect against meningitis and disseminated TB in children.

However, through the project, NIRT plans to study whether the kids and adolescents who live in close proximity to TB patients fare better later in life after receiving a BCG booster.

“What we're trying to do is to examine whether they develop or the breakdown into TB after getting the revaccination because what we have seen is at some time point, BCG-induced immunity comes down,” said Dr Padmapriyadarsini C, director, NIRT under the Indian Council of Medical Research.

“Maybe a booster dose of BCG can help but since we don’t know at what age will it help—we are planning a study on a wide range of age, spanning 6-18 years,” she said.

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The NIRT director added that previous studies have shown a spike in TB cases, caused due to mycobacterium tuberculosis bacteria, in adolescents and adults when they start going to college or work and are more exposed to the outside world.

Study on anvil

The proposed study says that there is considerable uncertainty on BCG revaccination and while it is known that BCG revaccination enhances immune responses, it is yet to be established if BCG revaccination can help prevent TB disease in household contacts.

“The primary aim of this study is to assess the efficacy of BCG revaccination compared to oral chemoprophylaxis in preventing TB disease in household contacts aged 6-18 years,” according to the study detail listed on the Clinical Trial Registry of India.

The study is designed as a multicentre randomised controlled trial with two groups of healthy household contacts receiving either the BCG vaccine or oral chemoprophylaxis.

The participants will be followed up for two years to compare the incidence of TB in each arm.

India’s tuberculosis challenge

As per the annual TB report released in March this year, the country recorded a total of 19,33,381 new and relapsed tuberculosis patients in 2021 marking a rise of 19 percent over the previous year.

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The report also said that 4.93 lakh deaths, excluding HIV patients, had been registered due to the infectious disease in India in 2020, which was 13 percent higher than the previous year.

India reports the highest number of TB cases globally, comprising over 26 percent of total cases and 34 percent of the fatalities every year. Also, of the total TB cases registered every year, nearly 3-4 percent cases are multi-drug resistant (MDR-TB) or extensively drug resistant (XDR-TB).

A survey carried out by NIRT has also shown that the actual incidence of TB in India is 316 per 100,000 population and even though the country has set an ambitious target of eliminating the highly contagious disease by 2025, it looks like an uphill task.