New TB Vaccines Prove Safe in Large Indian Trial, but Fall Short on Broad Lung Protection

Published: April 11, 2026

NEW DELHI — In a landmark effort to curb one of the world’s oldest and deadliest infectious diseases, a large-scale Phase 3 clinical trial in India has confirmed that two new tuberculosis (TB) vaccines are safe for adults and children. However, the study, published this week in The BMJ, revealed a sobering reality: neither vaccine provided significant protection against pulmonary TB—the most common and infectious form of the disease that attacks the lungs.

The “PreVenTB” study, led by the Indian Council of Medical Research (ICMR), followed over 12,700 individuals who lived in close contact with TB patients. While the vaccines, VPM1002 and Immuvac, failed to meet their primary goal of preventing lung-based TB, they showed a “silver lining” by reducing the risk of extrapulmonary TB (TB outside the lungs) and preventing the progression of latent infections into active disease.

A Massive Undertaking in the Heart of the Epidemic

India bears the world’s heaviest TB burden, accounting for approximately 26% of all global cases. Despite a 21% decline in incidence over the last decade, the disease still claims roughly 300,000 lives annually in the country.

The PreVenTB trial was designed to find a successor or supplement to the century-old BCG (Bacillus Calmette-Guérin) vaccine. While BCG is highly effective at preventing severe TB in infants, its protective effects wane by adolescence, leaving adults vulnerable to the pulmonary forms that drive transmission.

Between July 2019 and December 2020, researchers enrolled household contacts of TB patients across 18 sites in six Indian states, including Delhi, Maharashtra, and Tamil Nadu. These participants are at extreme risk, with a 10% to 20% annual chance of developing the disease themselves.

The Candidates: Fortified Bacteria vs. Immunotherapy

The trial tested two distinct scientific approaches:

1. VPM1002: A genetically modified version of the BCG vaccine. Developed in Germany and licensed to the Serum Institute of India, it is designed to be more “visible” to the immune system, allowing immune cells to identify and kill TB bacteria more efficiently.

2. Immuvac (MIP): An inactivated whole-cell vaccine that uses a non-pathogenic bacterium (Mycobacterium indicus pranii) to stimulate a broad immune response.

Both vaccines were administered in two doses, one month apart. Over a 38-month follow-up period, 96.7% of the participants remained in the study, providing researchers with a robust dataset on how these vaccines perform in real-world, high-exposure environments.

Mixed Results: Safety Achieved, but Protection Limited

The safety data was the trial’s most consistent success. Both vaccines were well-tolerated across age groups ranging from six to over 60 years old. However, the efficacy data painted a more complex picture.

Key Efficacy Findings

The failure to prevent pulmonary TB—which accounts for 85% of cases—is a significant hurdle for public health officials. Without a vaccine that stops lung infections, breaking the chain of transmission remains difficult.

However, the 50.4% effectiveness of VPM1002 against extrapulmonary TB (EPTB) is a notable victory. EPTB can affect the lymph nodes, bones, or the brain (meningitis), and in adults aged 36–60, it often carries a higher mortality risk than the pulmonary form.

The “Nutrition Gap” and Expert Analysis

One of the most striking findings of the study was the impact of body weight on vaccine performance. Neither vaccine showed efficacy in participants who were underweight.

“The lack of protection in underweight participants highlights a critical intersection between infectious disease and social determinants of health,” says Dr. Sanjay Sarin, a former WHO TB consultant. “You cannot vaccinate your way out of a malnutrition crisis. For these vaccines to work, the host’s immune system must be supported by adequate nutrition.”

Dr. Madhukar Pai, a renowned TB expert at McGill University, noted in a commentary that while the results are mixed, they provide a roadmap for the future. “Safety confirmation is a vital first step for any mass deployment. While we still need ‘next-gen’ candidates like M72/AS01E to tackle pulmonary TB, VPM1002’s ability to curb extrapulmonary forms could save thousands of lives where diagnosis is often delayed.”

Public Health Implications: What This Means for You

For the general public, particularly those living in high-burden areas, the trial offers several practical takeaways:

• Screening is Essential: Because the vaccines were effective at preventing latent TB from becoming active, “household contact tracing”—testing everyone who lives with a TB patient—remains the most effective way to stop the disease early.

• Nutrition as Medicine: Maintaining a Body Mass Index (BMI) above 18.5 is a biological prerequisite for a strong immune response to these vaccines.

• The Role of Preventive Therapy: Until a highly effective pulmonary vaccine is available, doctors continue to recommend the “3HP” regimen (a short course of preventive antibiotics) for those with latent infections.

Limitations and the Path Forward

The study had limitations, including the exclusion of individuals with HIV or diabetes, who represent 5% to 10% of the TB-affected population in India. Additionally, the trial was powered to detect 50% efficacy; it is possible the vaccines have a more modest effect on pulmonary TB that this specific study was not large enough to confirm.

As the ICMR moves toward potential regulatory approvals, the focus is shifting toward “combination strategies.” This might involve using these vaccines alongside nutritional supplements or as boosters for the existing BCG shot.

While the “holy grail” of a universal TB vaccine remains elusive, the PreVenTB trial has moved the needle forward, proving that large-scale, rigorous science can be conducted in the heart of the epidemic to find the tools that will eventually end TB.

Reference Section

• https://www.ndtv.com/health/new-tb-vaccines-safe-but-may-not-protect-against-all-forms-of-infection-phase-3-study-11338531

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.