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Updated: Mar 31, 2020 20:14 IST

The Bacillus Calmette-Guérin (BCG) vaccine given to newborns and children to prevent childhood tuberculosis appears to offer protection against coronavirus disease (Covid-19), according to US researchers who analysed the wide variation in the intensity of the disease in different countries.

The new study found Covid-19 cases and deaths are higher in countries that do not have or have discontinued universal BCG vaccination of children, such as the US, Italy, Spain and France, compared to countries with universal and long-standing immunisation policies, such as India and China.

Covid-19 cases and deaths in the United States, Italy and Spain have outpaced China, which was the epicentre of the outbreak that was first detected in Wuhan city in early December.

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BCG vaccination significantly reduced deaths from Covid-19, with the strongest reductions in countries that established a BCG vaccination policy earlier, found the study, published in the preprint health sciences server, medRxiv. BCG vaccination benefits held after factoring in cultural norms, mitigation efforts, and health infrastructure.

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The study found a direct correlation between how early the policy was established and the elderly population that would be protected. “Countries that have a late start of universal BCG policy, such as Iran in 1984, also had high mortality, consistent with the idea that BCG protects the vaccinated elderly population. We also found that BCG vaccination also reduced the number of reported Covid-19 cases in a country,” said the study titled ‘Correlation between universal BCG vaccination policy and reduced morbidity and mortality for Covid-19: an epidemiological study’.

It recommends BCG vaccination as a potential new tool in the fight against Covid-19.

India started BCG vaccination of children in 1949, and currently 97% of 26 million children born in India receive the BCG vaccine free. India’s universal immunisation programme, under which the BCG vaccine is given, went up to the current figure of 97%, according to the ministry of health and family welfare data, up from 92% in 2015-16, as was recorded by the National Family of Health Survey 4. It is manufactured in India, and costs less than RS 100 per vial in the private sector.

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“BCG coverage is highest among all vaccines given to children under five years under the universal immunisation programme. It’s given to newborn babies at birth, or up to one year if vaccination is missed at birth,” said Dr Pradeep Haldar, deputy commissioner (immunisation), ministry of health and family welfare. Vaccination is above 95% across all states, including the empowered action states with universal immunisation coverage of less than 85%.

BCG vaccine contains a live, weakened strain of Mycobacterium bovis, a cousin of M. tuberculosis, which is the bacteria that causes tuberculosis.

“The BCG vaccine is an immunomodulator that boosts immune response to offer broad protection to respiratory infections. Even more protective is a vaccine from Mycobacterium indicus pranii (MIP), which has been isolated and sequenced in India National Institute of Immunology. It’s approved for use against leprosy and septicaemia, and PGI Chandigarh recently evaluated its translational application as an immunotherapeutic against severe acute respiratory syndrome (a coronavirus like Sars-Cov-2, the virus that causes Covid-19). The results have been sent for publication,” said Dr NK Ganguly, former director general, Indian Council of Medical Research.

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Australia, Netherlands, Germany and the United Kingdom have announced they will begin large-scale human trials to see whether BCG vaccination protects health workers from Covid-19 by triggering an immune response to reduce symptoms, prevent severe illness or prevent infection.

Australia announced on Friday that it will begin BCG vaccine trials with around 4,000 physicians and nurses, who are at higher risk of becoming infected with the respiratory disease than the general population, and in older persons, who are at higher risk of serious illness.

Netherlands has recruited around 1,000 healthcare workers in eight Dutch hospitals to either receive the BCG vaccine or a placebo.

“BCG vaccination produces non-specific immune effects that have been shown to boost response against non-mycobacterial pathogens, and using it to improving innate immunity against Covid-19 would buy time to develop a specific vaccine against the disease,” said a scientist from the Indian Council for Medical Research, requesting anonymity.

BCG vaccination significantly increases the secretion of pro-inflammatory cytokines, specifically IL-1B, which play a vital role in antiviral immunity.

“BCG vaccination has been shown to produce broad protection against viral infections and sepsis, raising the possibility that the protective effect of BCG may be associated co-occurring infections and sepsis-related deaths,” said Dr Ganguly.

The broad use of the BCG vaccine across a population could reduce the number of carriers, and combined with other measures, could act to slow down or stop the spread of Covid-19, according to the US study.

The study answers why Covid-19 spread in China despite children getting BCG vaccinated since the 1950’s. “During the Cultural Revolution (1966-1976), tuberculosis prevention and treatment agencies were disbanded and weakened. We speculate that this could have created a pool of potential hosts that would be affected by and spread Covid-19,” said the study.