BCG vaccine: 100 years and counting

Q  Why is it in News ? 

A    The first use of BCG (Bacillus Calmette-Guerin), the vaccine against tuberculosis (TB) in humans has been completed for 100 years.

Q What is Tuberculosis (TB)?

A 

• TB is a very ancient disease and has been documented to have existed in Egypt as early as 3000 BC.
• It 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).

Q Why it is not yet eliminated ? 

A 

• Other historically dreaded diseases like smallpox, leprosy, plague and cholera have been either eradicated or controlled to a large extent due to advances in science and technology.
• However, TB continues to be a major public health problem in the world.
• 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.

Q What is BCG Vaccine for TB? 

A

• 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.
• India is committed to eliminate TB as a public health problem by 2025.

Q How much is effectiveness of BCG ? 

A 

• One intriguing fact about 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.
• 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%.
• 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.