EXPLORING INDIA’S INITIATIVES ON BCG REVACCINATION

TAG: GS 3: SCIENCE AND TECHNOLOGY

THE CONTEXT: Twenty-three States have consented to participate in the BCG revaccination study in adults that will be undertaken in a “programme implementation study mode” to evaluate the effectiveness of the vaccine in reducing TB disease incidence.

EXPLANATION:

• The initiative to conduct a BCG (Bacille Calmette-Guérin) revaccination study in adults has stirred considerable discussion and debate due to the absence of comprehensive clinical trials in the country.
• The study aims to assess the effectiveness of the BCG vaccine in reducing Tuberculosis (TB) disease incidence, primarily targeting high-risk groups such as individuals older than 50 years, those with prior TB disease, underweight adults, diabetics, smokers, and alcohol consumers.

Lack of Prior Clinical Trials in India:

• India has not conducted clinical trials to ascertain the efficacy of BCG revaccination in adults for preventing TB disease.
• However, two clinical investigation studies by St. John’s Research Institute in Bengaluru have indicated the significant immunogenicity of BCG revaccination in adults.

Expert Committee Recommendations and Government Approach:

• An expert committee, including formerly of the WHO, recommended a comprehensive trial before implementation at the population level.
• Nevertheless, the Indian government has chosen a program implementation study over a clinical trial due to concerns regarding the lengthy trial process.
• This approach involves using some districts as intervention arms and others as control arms to capture TB incidence over a couple of years.

WHO’s Standpoint on BCG Revaccination:

• The WHO currently does not advocate for programmatic or pilot BCG revaccination, even in high TB burden countries like India.
• Their 2018 BCG vaccine position paper emphasizes that repeat BCG vaccination shows minimal or no additional benefit against TB or leprosy.

Challenges and Limitations of Previous Studies:

• The protective effect of a single dose of BCG vaccine given to infants in India wanes within a short time.
• The Chingleput BCG revaccination study in 1968, involving a small sub-group, indicated a 36% efficacy in reducing TB incidence after 15 years, but this study had limitations in sample size and knowledge gaps about confounding factors.

Proposed Methodology and Participating States:

• The study intends to follow a phase 4-like pragmatic evaluation by earmarking districts in participating states as intervention and control arms.
• States such as Uttar Pradesh, Madhya Pradesh, and Tamil Nadu have agreed to participate.
• Tamil Nadu planned to study lakhs of consenting participants and closely monitor a few thousand individuals for vaccine efficacy over two to three years.

Challenges Faced by Non-Participating States:

• Some states like Kerala, Bihar, Chhattisgarh, West Bengal, and Uttarakhand have chosen not to participate in the study due to field constraints and existing gaps in their immunization programs, which could overburden the staff involved.
• In essence, the BCG revaccination study in adults across various Indian states represents a shift from the usual clinical trial method to a program implementation study mode.
• This approach aims to evaluate the effectiveness of BCG revaccination in high-risk groups despite the reservations and recommendations from global health authorities like the WHO.

BCG VACCINE:

• Bacillus Calmette-Guerin (BCG) is the live attenuated vaccine form of Mycobacterium bovis used to prevent tuberculosis and other mycobacterial infections.
• The vaccine was developed by Calmette and Guerin and was first administered to human beings in 1921.
• BCG is the only vaccine against tuberculosis.
• It is the most widely administered vaccine and usually a part of the routine newborn immunization schedule.
• BCG vaccine also offers protection against non-tuberculous mycobacterial infections like leprosy and Buruli ulcer.

SOURCE: https://www.thehindu.com/sci-tech/bcg-revaccination-study-in-high-risk-adults-to-begin-in-23-states/article67594580.ece/amp/