BCG Vaccine

BCG Vaccine

Subject – Science and Tech

Context – BCG vaccine: 100 years and counting

Concept –

• BCG (Bacillus Calmette-Guerin) is the vaccine against tuberculosis (TB) in humans.
• TB is caused by a bacterium called Mycobacterium tuberculosis, belonging to the Mycobacteriaceae family consisting of about 200 members.
• Some of these cause diseases like TB and leprosy in humans and others infect a wide range of animals.
• Mycobacteria are also widely dispersed in the environment.
• In humans, TB most commonly affects the lungs (pulmonary TB), but it can also affect other organs (extra-pulmonary TB).
• TB is a very ancient disease and has been documented to have existed in Egypt as early as 3000 BC.
• According to the WHO’s Global TB Report, 10 million people developed TB in 2019 with 1.4 million deaths. India accounts for 27% of these cases.
• BCG was developed by two Frenchmen, Albert Calmette and Camille Guerin, by modifying a strain of Mycobacterium bovis (that causes TB in cattle) till it lost its capacity to cause disease while retaining its property to stimulate the immune system. It was first used in humans in 1921.
• Currently, BCG is the only licensed vaccine available for the prevention of TB. It is the world’s most widely used vaccine with about 120 million doses every year and has an excellent safety record.
• In India, BCG was first introduced in a limited scale in 1948 and became a part of the National TB Control Programme in 1962.
• BCG is that it works well in some geographic locations and not so well in others.
• Generally, the farther a country is from the equator, the higher is the efficacy. It has a high efficacy in the UK, Norway, Sweden and Denmark; and little or no efficacy in countries on or near the equator like India, Kenya and Malawi, where the burden of TB is higher. These regions also have a higher prevalence of environmental mycobacteria.
• However, in children, BCG provides strong protection against severe forms of TB. This protective effect appears to wane with age and is far more variable in adolescents and adults, ranging from 0–80%.
• India is committed to eliminate TB as a public health problem by 2025.
• Over the last ten years 14 new vaccines have been developed for TB and are in clinical trials.
• In addition to its primary use as a vaccine against TB, BCG also protects against respiratory and bacterial infections of the newborns, and other mycobacterial diseases like leprosy and Buruli’s ulcer. It is also used as an immunotherapy agent in cancer of the urinary bladder and malignant melanoma.
• In progress Interestingly, it has been observed that in some countries that have had BCG vaccination as a national policy, the burden of SARS CoV¬2 morbidity and mortality was significantly less compared to countries which did not.