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Mahesh

03/12/23 09:07 AM IST

BCG revaccination study in high-risk adults to begin in 23 States

In News
  • 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.
Efficacy of BCG vaccination
  • 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.
  • Most studies of BCG revaccination globally have not found major impacts on reducing TB incidence. Therefore, it is not recommended by the WHO currently.
  • Studies have shown minimal or no evidence of any additional benefit of repeat BCG vaccination against TB or leprosy. Therefore, revaccination is not recommended.
  • The protective effect of a single dose of the vaccine given to infants in India wanes within a short time.
  • A 15-year follow-up study found that at the end of 7.5 years there was “complete lack of protective efficacy” in children. Even if revaccination offers protection in adults, the duration of protection remains to be seen.
  • In the 1968 trial, 2,890 adults received a BCG revaccination and 1,546 did not, and the efficacy of the vaccine to reduce TB incidence was found to be 36%.
  • But the protective efficacy was seen only at the end of 15 years of follow-up, and the protective effect of BCG revaccination was significant only in the 31-40 years age group.
limitations of the study
  • The sample size is small, potential confounders such as nutritional status, diabetes, smoking and alcohol consumption, and TB exposure status are not known, and the time interval between the first dose and BCG revaccination is also not known.
  • Tamil Nadu, which has consented to participate in the study, has 44 TB districts. Half of these will be earmarked as intervention arm and the remaining as control. “Since adults belonging to high-risk groups are to be studied, the number of consenting participants will run into lakhs.
  • Kerala, Bihar, Chhattisgarh, West Bengal and Uttarakhand that have not consented to participate in the study.
Source- The Hindu

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