Bacillus Calmette-Guerin: BCG vaccine

Context:

100years has passed since the Bacillus Calmette–Guérin (BCG vaccine) was introduced to combat tuberculosis (TB) on 18 July, 1921.

About BCG vaccine:

• The Bacillus Calmette-Guérin (BCG vaccine) is a live attenuated strain derived from an isolate of Mycobacterium Bovis.
• A live attenuated vaccine means that it uses a pathogen whose potency as a disease producer has been artificially disabled, but whose essential identifying characteristics which help the body to increase an immune response to it have been left unchanged.
•  It has been used widely across the world as a vaccine for tuberculos
• BCG was developed by modifying a strain of Mycobacterium bovis (that causes TB in cattle). 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.
• In children, BCG provides strong protection against severe forms of TB. This protective effect is far more variable in adolescents and adults, ranging from 0–80%.
• 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.

India and BCG Vaccine:

• In May 1948, the Government of India issued a press note stating that tuberculosis was ‘assuming epidemic proportions’ in the country.
•  The Government decided to introduce BCG vaccination on a limited scale as a measure to control the disease.
•  A BCG Vaccine Laboratory at King Institute, Guindy, Madras (Chennai) was set up in 1948.
•  In August 1948, the first BCG vaccinations were conducted in India.
• By 1955-56, the mass campaign had covered all states of India.
•  BCG remains part of the basket of vaccines included in the Universal Immunisation Programme.

Varying Efficacy of BCG

• BCG 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 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.It is believed that these may interfere with the protective effect against TB.

Rates of protection against TB infection vary widely and protection lasts up to twenty years. Among children it prevents about 20% from getting infected and among those who do get infected it protects half from developing disease. The vaccine is given by injection into the skin. There is no evidence that additional doses are beneficial.

Serious side effects are rare. Often there is redness, swelling, and mild pain at the site of injection. A small ulcer may also form with some scarring after healing. Side effects are more common and potentially more severe in those with poor immune function. It is not safe for use during pregnancy. The vaccine was originally developed from Mycobacterium bovis, which is commonly found in cows. While it has been weakened, it is still live.

The BCG vaccine was first used medically in 1921. It is on the World Health Organization’s List of Essential Medicines. As of 2004, the vaccine is given to about 100 million children per year globally.

What is tuberculosis (TB)?

• TB is caused by a bacterium called Mycobacterium tuberculosis, belonging to the Mycobacteriaceae family.
• In humans, TB most commonly affects the lungs (pulmonary TB), but it can also affect other organs (extra-pulmonary TB).
• Unlike other historically dreaded diseases like smallpox, leprosy, plague and cholera that have been either eradicated or controlled to a large extent, 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.

Way Forward

• India is committed to eliminate TB as a public health problem by 2025. To achieve this goal, we would not only need better diagnostics and drugs but also more effective vaccines.
• We need to build on lessons learnt from the COVID-19 pandemic, and replicate the successes achieved especially in vaccine development and prepare to address the challenges faced in ensuring vaccine equity.

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