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New Delhi — In a significant development affecting India’s ambitious tuberculosis (TB) elimination goals, the Central Drugs Standard Control Organisation (CDSCO) has flagged major discrepancies in the clinical trial data submitted by the Serum Institute of India (SII) for its novel Recombinant BCG (rBCG) vaccine.
The Subject Expert Committee (SEC) of the CDSCO, in a recent meeting, declined to progress the approval process for the vaccine, citing that the evidence presented was “neither adequate nor conclusive.” The committee specifically noted that the submission relied heavily on “post-hoc analyses”—statistical interpretations made after a trial has concluded—rather than meeting the pre-defined primary objectives of the studies.
The Core Issue: Weak Evidence and Statistical Gaps
The Serum Institute of India, the world’s largest vaccine manufacturer, had sought permission to manufacture and market the rBCG vaccine (VPM1002) for two specific indications: preventing extra-pulmonary tuberculosis in individuals aged 6 years and older, and preventing pulmonary tuberculosis in children and adolescents aged 6 to 18.
However, the regulatory panel found that the data from two major clinical studies did not support these claims with sufficient statistical rigour.
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Study 1 (Prevention of Recurrence): This Phase II/III trial aimed to see if the vaccine could prevent TB from returning in patients who had already been cured. The results showed that the vaccine failed to meet its primary endpoint. The difference in efficacy between the vaccine and a placebo was 13.5% for all TB recurrence cases and only 7.8% for bacteriologically confirmed cases—numbers that were not statistically significant.
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Study 2 (Household Contacts): This Phase III trial, conducted by the Indian Council of Medical Research (ICMR), compared VPM1002 against another vaccine (Immuvac) and a placebo in healthy people living with TB patients. The overall vaccine efficacy against all confirmed TB cases was a low 16.9%, which was statistically non-significant.
The panel criticized the firm’s attempt to claim a 50.4% efficacy against Extra-Pulmonary TB (EPTB) by recalculating data using only two arms of the study (Vaccine vs. Placebo) instead of the originally designed three-arm structure. The SEC noted, “The statistically non-significant result was interpreted and concluded as statistically significant by calculating two-arm data instead of three-arm data… The primary objective of the study was not met.”
Understanding “Post-Hoc Analysis”
For the general public, the term “post-hoc analysis” is crucial to understanding this rejection. In clinical trials, scientists set a specific goal (primary endpoint) before the study begins—for example, “reduce TB cases by 50%.”
If the trial fails to meet this goal, researchers sometimes look back at the data to find any positive patterns in subgroups (e.g., “it didn’t work for everyone, but it worked for this specific age group”). This is post-hoc analysis. While it can generate new hypotheses, regulators generally consider it weak evidence for drug approval because it increases the risk of finding coincidental positives (“cherry-picking” data).
“Regulatory bodies are the gatekeepers of public safety,” explains Dr. Anjali Mehta (name changed for general context), a clinical research consultant not involved in the trial. “Approving a vaccine based on retrospective data slicing sets a dangerous precedent. If the primary goal failed, we cannot simply shift the goalposts after the match is over.”
Scientific Context: The Promise of VPM1002
The vaccine in question, VPM1002, is a genetically modified version of the century-old Bacillus Calmette-Guérin (BCG) vaccine. Standard BCG is effective in protecting infants from severe forms of TB but wanes in effectiveness against the most common form—pulmonary TB in adults.
VPM1002 was engineered to be more effective by modifying the bacteria to “escape” the immune system’s containment (phagosome) inside cells, theoretically triggering a stronger and broader immune response. It was viewed as a potential game-changer for India, which bears the world’s highest TB burden.
Public Health Implications
The rejection represents a setback for India’s “End TB by 2025” roadmap. According to the World Health Organization’s Global Tuberculosis Report 2024, India accounted for 25% of the global TB burden. While incidence is declining, the lack of an effective adult vaccine remains a massive gap in the eradication strategy.
“We desperately need a new tool,” says a senior pulmonologist from a government hospital in New Delhi. “Treating latent TB and active cases is like mopping the floor while the tap is still running. An effective vaccine would turn off the tap. However, that vaccine must be proven effective beyond doubt. A vaccine that offers false security could derail our control programs.”
What Happens Next?
The SEC has recommended that Serum Institute conduct a new, “adequately powered study” based on the secondary findings of the ICMR trial to provide conclusive evidence.
This recommendation essentially sends the vaccine back to the clinical trial phase, likely delaying any potential rollout by several years. It underscores the CDSCO’s increasing vigilance in ensuring that “Made in India” biomedical innovations meet global standards of evidence-based medicine.
The meeting minutes also noted that several high-profile experts, including Dr. Urvashi B. Singh (Dy. DG TB) and Dr. Srinath Satyanarayana (Director, ICMR-NIRT), recused themselves from the decision-making process due to declared conflicts of interest, ensuring the integrity of the panel’s conclusion.
Medical Disclaimer
Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.
References
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Primary Source: CDSCO Subject Expert Committee (SEC) Meeting Minutes. “Recommendations of the SEC (Vaccine) meeting regarding Recombinant BCG (rBCG) Vaccine data.” Central Drugs Standard Control Organisation, Government of India. Accessed December 2025 via Medical Dialogues.
