A tuberculosis vaccine may help reduce the risk of death from novel coronavirus, according to two peer-reviewed studies released last week. According to the authors of the study, developing countries, where TB vaccine was given on higher rates, have lower-than-expected COVID-19 death rates.
One of the studies led by Indian researchers from the Jawaharlal Nehru University (JNU) stated that the quality of protection from COVID-19 depends upon the TB vaccine strain, the Hindustan Times reported. The widely-used TB vaccine-Bacillus Calmette-Guerin (BCG) has six major strains Pasteur, Danish, Glaxo 1077 (derived from the Danish strain), Tokyo, Russia, and Moreau.
Gobardhan Das, chairperson, Centre for Molecular Medicine at JNU said that BCG has offered some degree of protection against COVID-19, but all the countries (that give BCG vaccines to their children) did not do equally well. Das added that BCG Mix, BCG Pastuer, and BCG Tokyo do better compared to others, such as BCG Russia and BCG Danish. In India, BCG Mix vaccine is used.
The peer-reviewed study was published in Cell Death and Disease.
In India, BCG vaccination of children started in 1949. In 2019, at least 97 per cent of the 2.6 crore children received the TB vaccine. The vaccine in children prevents a simple TB from turning into a systemic and affecting the brain and other organs. However, it doesn't offer protection from adult pulmonary TB, which has led to several countries discontinuing its use. Das said that BCG also had protective effects against leprosy, buruli ulcer, bladder cancer, type-1 diabetes and several other diseases.
The World Health Organisation (WHO) in April said that there was no evidence that BCG protected people against coronavirus.
According to the daily, many clinicians and epidemiologists were also unconvinced about the findings. Dr Krishnan Chhugh, director of pediatrics at Fortis Memorial Research Institute said that it was highly unlikely that the protection would last till adulthood. "The vaccine just prevents simple TB from becoming systemic and affecting the brain and other organs," says Chugh.
Also, epidemiologists are wary that most countries with high BCG vaccination rates, like India and Brazil, are not testing enough. Prof Madhukar Pai, Director, McGill University, Montreal, said that it was dangerous to make conclusions in such a dynamic situation. Pai tweeted, "We simply cannot act on these correlations and must wait for randomised trials on BCG and COVID-19".