The Bacillus Calmette-Guérin (BCG) vaccine to prevent tuberculosis must be administered to health care workers and the elderly as prophylaxis (preventive action) for the coronavirus disease (Covid-19), according to a paper published in the Indian Journal of Orthopaedics.
“BCG vaccine is known to confer a broad-spectrum immunity not just against tuberculosis but other diseases. Indians are already administered BCG as part of our immunisation programme, but other countries, where it has been stopped, might use BCG vaccine prophylaxis along with chloroquine that is now being used. It is already tested in humans and widely available,” said Dr Ajay Gupta, the author of the article and orthopaedic surgeon from Maulana Azad Medical College.
Immunity conferred through BCG vaccine may be effective in preventing a cytokine storm, the article suggests. A cytokine storm is when the immune system goes into an overdrive and starts attacking the body’s own cells and tissues other than fighting off an infection.
“Viral-specific CD8 T cells (of key importance to the immune system) were seen to have special affinity towards BCG-induced granulomas (a collection of immune cells) resulting in substantial accumulation of viral-specific CD8 T cells there. Such an affinity can be made to be used in patients with COVID-19 to divert and subvert its overactive immune response towards BCG granulomas,” the study reads.
“This basically means that BCG-induced immune response might reduce the chances of cytokine storms, which is what leads to deaths in such viral infections,” said Dr Gupta. “However, the immune response is generated six to ten weeks after the vaccine is given. In the meantime, for immediate protection already available, oral salmonella vaccine may be used to boost Th1 immunity,” he added.Th1 immunity refers to immunity against intracellular parasites.
{{/usCountry}}“This basically means that BCG-induced immune response might reduce the chances of cytokine storms, which is what leads to deaths in such viral infections,” said Dr Gupta. “However, the immune response is generated six to ten weeks after the vaccine is given. In the meantime, for immediate protection already available, oral salmonella vaccine may be used to boost Th1 immunity,” he added.Th1 immunity refers to immunity against intracellular parasites.
{{/usCountry}}“There is no concrete evidence to suggest that BCG-vaccine will protect against the viral infection, but it is a hypothesis that needs to be studied by comparing robust data from places where the vaccine is administered and where it is not. However, BCG-vaccine is a known immune-modulator,” said Dr Shobha Broor, former head of department of microbiology at the All India Institute of Medical Sciences.
Australia, for instance, has embarked on a large clinical study of the BCG vaccine among health workers.
Apart from looking at immune-modulation through available vaccines, the article also suggests that natural exposure to mycobacterium (tuberculosis), Salmonella (Typhoid), and influenza can boost the immune system resulting in less severe infections and deaths due to Covid-19.
“COVID-19 has been seen to affect more of those countries who have robust and free influenza vaccination program leading to reduced natural flu infection among their population,” the article reads.
“Countries where flu vaccines are readily available have witnessed a bad course of the infection. This might be because in the absence of natural flu infection, the mucous membrane is unable to develop the innate immunity that is effective against all kinds of pathogens,” said Dr Gupta.
To study the impact of the natural infections on the course of Covid-19, Dr Gupta’s team will do immune profiling of 20 Covid-19 patients who have severe disease, 20 who have mild symptoms, and 20 people who haven’t had the infection. The team has received an ethical clearance for the study.