Context

The Bacillus Calmette-Guerin (BCG) vaccine, administered to millions of Indian children soon after birth to protect against tuberculosis, could be a "game-changer" in the fight against the deadly coronavirus, say US scientists.

About

• BCG, or bacille Calmette-Guerin, is a vaccine for tuberculosis (TB) disease. BCG vaccine has a documented protective effect against meningitis and disseminated TB in children.
• It is 70-80% effective against the most severe forms of TB, such as TB meningitis. However, it is less effective in preventing the form of TB that affects the lungs.
• The vaccine prevents infant deaths from a variety of causes, and sharply reduces the incidence of respiratory infections.
• It does not prevent primary infection and, more importantly, does not prevent reactivation of latent pulmonary infection, the principal source of bacillary spread in the community.
• The impact of BCG vaccination on transmission of Mtb is therefore limited.
• The biological interaction between Mtb and the human host is complex and only partially understood.
• The bacille Calmette-Guerin (BCG) vaccine has existed for 100 years. The weakened virus was first used in humans in 1921 and was widely adopted after World War II.

How does it stimulate the immune system?

• The BCG vaccine contains live bacteria that have been weakened (attenuated), so that they stimulate the immune system but do not cause disease in healthy people.
• The vaccine seems to “train” the immune system to recognize and respond to a variety of infections, including viruses, bacteria and parasites.
• However the vaccine should not be given to people who are clinically immunosuppressed (either due to drug treatment or underlying illness).
• This is because the vaccine strain could replicate too much and cause a serious infection. This includes babies whose mothers have had immunosuppressive treatment while they were pregnant or breastfeeding.
  
  

Can it treat Coronavirus?

• Like other vaccines, BCG has a specific target: TB. But evidence accumulating over the past decade suggests the vaccine also has so-called off-target effects, reducing viral illnesses, respiratory infections and sepsis, and appears to bolster the body’s immune system.
• The idea is an offshoot of the “hygiene hypothesis,” which suggests that the modern emphasis on cleanliness has deprived children of exposure to germs.
• The lack of “training” has resulted in weakened immune systems, less able to resist disease.
• A recent review by the World Health Organization concluded that BCG had beneficial “off-target effects,” and recommended doing more trials of the vaccine against a wider range of infections.

What the study has found?

• The study has found that countries without universal policies of BCG vaccination, such as Italy, the Netherlands, and the United States, have been more severely affected compared to countries with universal and long-standing BCG policies.
  
  

  India & BCG: The BCG vaccine is part of India's universal immunisation programme and administered to millions of children at birth or soon after it. It is the live weakened form of mycobacterium bovis -- the causative agent of tuberculosis in cattle -- related to mycobacterium tuberculosis, the bacteria which causes tuberculosis in humans. India, with the world's highest TB burden, introduced BCG mass immunisation in 1948.

  
  
  
• According to the study, a combination of reduced morbidity and mortality could make the BCG vaccination a game-changer in the fight against coronavirus.
• The BCG vaccine is part of India's universal immunisation programme and administered to millions of children at birth or soon after it.
• It is the live weakened form of mycobacterium bovis -- the causative agent of tuberculosis in cattle -- related to mycobacterium tuberculosis, the bacteria which causes tuberculosis in humans .