Source: DD news
Subject: Science and Technology
Context: India has delivered 13 tonnes of Bacille Calmette-Guérin (BCG) vaccines and related materials to Afghanistan’s Ministry of Public Health.
About Bacille Calmette-Guérin (BCG) Vaccine:
What it is?
- The BCG vaccine is a live attenuated (weakened) vaccine primarily used to provide protection against Tuberculosis (TB). It is the only licensed vaccine available against TB and is one of the most widely administered vaccines in the world, typically given to newborns.
Developed By: It was developed by French scientists Albert Calmette and Camille Guérin at the Pasteur Institute. After 13 years of research, it was first administered to humans in 1921.
Aim:
- To prevent severe forms of childhood TB, such as TB meningitis and disseminated TB.
- To reduce the overall global burden of tuberculosis, especially in endemic regions.
- To provide cross-protection against other mycobacterial diseases like Leprosy and Buruli ulcer.
Components of the Vaccine:
- Active Ingredient: A live attenuated strain of Mycobacterium bovis, a bacterium that causes TB in cattle but is weakened for human use.
- Excipients: Typically includes stabilizers like glycerol, citric acid, and various salts (sodium, potassium, magnesium) to maintain potency.
- Dry Materials: As seen in the Afghanistan shipment, the vaccine is often supplied in a freeze-dried (lyophilized) form requiring diluents for reconstitution.
How it Works?
- The vaccine introduces a weakened form of the bacteria into the body, which primes the immune system to recognize mycobacterial proteins.
- This stimulates the production of T-cells and antibodies without causing the disease itself. Upon future exposure to Mycobacterium tuberculosis, the immune system can mount a rapid and effective defense.
Key Features
- Administration: Injected intradermally (into the skin), usually in the upper left arm.
- The BCG Scar: A common and expected feature where a small blister or ulcer forms at the injection site, eventually leaving a permanent flat scar.
- Target Population: Most effective when given to infants and young children in countries with high TB prevalence.
- Treatment Use: Beyond prevention, it is used as a form of immunotherapy to treat certain types of bladder cancer.
Significance:
- It remains the foundation of TB prevention programs, helping to drastically reduce childhood mortality related to TB meningitis.
- For nations like India, providing BCG vaccines is a critical tool of vaccine diplomacy, fostering international solidarity and supporting fragile health systems.
- It offers 70–80% protection against the most severe forms of TB in children, though its effectiveness against adult pulmonary TB is more variable.
