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. The study will target some high-risk groups — those older than 50 years, prior TB disease, underweight adults, diabetics, and those who smoke and consume alcohol. The phase-1 of the study will be conducted in Uttar Pradesh and Madhya Pradesh, says a Delhi-based official.
No clinical trials have been carried out in India to study the efficacy of BCG revaccination in adults to prevent TB disease, and studies in other countries have thrown up mixed results. Two clinical investigation studies (2019 and 2023) by St. John’s Research Institute, Bengaluru have found BCG revaccination in adults to be significantly immunogenic.
Despite the recommendation of an expert committee that a clinical trial be carried out first, the government has decided to go ahead with the programme implementation study. “An expert committee constituted by ICMR recommended that a robust trial be carried out in India and implementation at population-level be undertaken once evidence of efficacy was available,” says Dr. Soumya Swaminathan, former Chief Scientist at WHO and a member of the expert committee. “Most studies of BCG revaccination globally have not found major impacts on reducing TB incidence. Therefore, it is not recommended by the WHO currently. However, a recent phase-2 trial in South Africa suggested it may prevent TB infection. Hence, further trials are warranted to assess the effectiveness of BCG revaccination in different populations, age groups, by timing of revaccination and types of TB.”
