The development of tuberculosis (TB) vaccines faces challenges due to the complex immune response in humans, immature animal models for assessing vaccine efficacy, and the prolonged course from TB infection to the development of active TB disease, requiring extensive and lengthy clinical research for validation.
On March 19, 2024, the Bill & Melinda Gates Medical Research Institute (hereafter referred to as "Gates Medical Research Institute") announced the initiation of Phase III clinical trials for the TB candidate vaccine M72/AS01E. The first batch of vaccinations will be conducted in South Africa, severely affected by TB. If proven safe and effective, M72 could become the first vaccine for preventing the most common form of TB in adolescents and adults.
Currently, only the Bacillus Calmette-Guérin (BCG) vaccine is effective for newborns, ideally administered within 24 hours of birth. There is still no effective TB prevention vaccine for adults worldwide.
TB vaccine development faces significant challenges? March 24, 2024, marked the 29th World Tuberculosis Day, and today, let's delve into this matter.
TB is a chronic infectious disease caused by Mycobacterium tuberculosis. Except for hair and teeth, all other organ systems in the human body can be infected, leading to illness. Tuberculosis mainly affects the lungs, with pulmonary TB accounting for over 80% of all types of TB, making it the primary form of the disease.
Clinical manifestations of pulmonary TB include coughing up blood, bloody sputum, weight loss, and fatigue. The main mode of transmission is through respiratory droplets. When patients cough, sneeze, or speak loudly, large quantities of bacteria-containing droplets are released into the air, potentially infecting others. According to statistics from the Shanghai Municipal Health Commission, in 2023, Shanghai registered 5,303 cases of pulmonary TB, with an incidence rate of 21.1 per 100,000 population.
Dr. Wang Li, a respiratory physician specializing in TB at Tongji University Affiliated Shanghai Pulmonary Hospital, explained that current treatment for pulmonary TB primarily involves chemotherapy, adhering to principles of early, combined, appropriate, regular, and full-course drug use, supplemented by traditional Chinese medicine and immunotherapy. The treatment regimen for the majority of patients consists of oral medications, with inhalation therapy used for those with bronchial TB. In addition to internal medicine treatments, a small number of patients may require bronchoscopy intervention and surgical procedures.
Furthermore, pulmonary TB has a tendency to relapse. Dr. Wang Li stated that there are many factors influencing relapse, with improper medication being a significant cause. "In addition, poorly controlled diabetes, use of corticosteroids, and immunosuppressants are all high-risk factors for TB relapse. Long-term sleep deprivation, irregular diet, excessive weight loss leading to malnutrition can also increase the likelihood of relapse." Dr. Wang Li emphasized the importance of seeking medical attention at specialized hospitals for standardized anti-TB treatment and regular follow-ups after a TB diagnosis, advising against arbitrary changes, discontinuation, or reduction of medication, which can effectively reduce the risk of TB relapse.
Since eradicating the disease is challenging, can proactive interventions be implemented at the prevention stage? However, why is TB vaccine development so difficult?
Dr. Wang Li explained that vaccines work by inducing long-term effective immune memory in the body and maintaining stable response intensity to provide protection. "TB vaccine development is constrained by the complexity of the human immune response, immature animal models for assessing vaccine efficacy, and the lengthy course from TB infection to active TB disease, necessitating extensive and prolonged clinical research for validation."
While awaiting the efforts of medical professionals, ordinary individuals can also take proactive measures in daily life to protect themselves as much as possible. Dr. Wang Li emphasized that TB prevention involves three key aspects: firstly, controlling sources of infection by diagnosing and treating patients promptly, especially those with positive sputum cultures, while maintaining good hygiene practices such as refraining from spitting in public spaces; secondly, since TB is transmitted through respiratory droplets and aerosols, families of patients should ensure good ventilation and disinfect sputum, with close contacts undergoing regular screenings; thirdly, infants should receive the BCG vaccine, while the elderly and immunocompromised individuals should focus on improving nutrition and engaging in physical exercise. Prompt medical attention should be sought if symptoms such as coughing up blood, persistent cough with sputum for more than two weeks, night sweats, fatigue, or blood in sputum are experienced.
