Chennai: The Bacillus Calmette-Guerin (BCG) vaccine, used in India to prevent tuberculosis, can modify disease outcomes in elderly Covid patients by reducing the exaggerated immune response that often leads to higher mortality, an ongoing trial by National Institute for Research on Tuberculosis (NIRT) has found.
All Covid vaccines currently in use across the world are disease-modifying and not disease-preventing.
Dr Subhash Babu, scientific director at NIH-International Centers for Excellence in Research, who is part of the study, said: “We have found in our study that in the elderly, BCG somehow reduces the exaggerated immune response that leads to adverse Covid outcomes.”
He added, “We are not sure exactly how that happens because the vaccine is known to stimulate the immune system.”
The study by NIRT — which comes under the Indian Council of Medical Research (ICMR) — is looking at the effect of the BCG vaccine when people aged between 60 and 95 years contract Covid. The total sample size is 1,450.
The rationale behind the trial, as submitted to the Clinical Trials Registry of India, states: “SARS-CoV2 viral infection is spreading rapidly throughout the world. A large epidemic in India poses a major threat to the public health system. Elderly individuals, especially those with diabetes, hypertension and other chronic diseases, are especially at high risk of mortality. Strategies to protect these individuals are, therefore, desperately needed to safeguard continuous patient care.”
The statement adds that BCG is a vaccine against tuberculosis, “with protective non-specific effects against other respiratory tract infections in in-vitro and in-vivo studies, and reported significant reductions in morbidity and mortality”.
“Based on the capacity of BCG to reduce the incidence of respiratory tract infections in children and adults, to exert antiviral effects in experimental models; and to reduce viremia in an experimental human model of viral infection, the hypothesis is that BCG vaccination will partially protect against mortality in high-risk, elderly individuals.”
Babu pointed out that the NIRT trial results are currently in the process of being published so they are confidential, but the outcome has been encouraging.
The trial results are in contrast to what researchers from South Africa reported in The Lancet in May 2022 — that the BCG vaccine when administered to healthcare workers did not seem to modify the severity of Covid.
Calming cytokine storm
According to Babu, multiple studies by his department — some of them published — have established a definite role of BCG in calming the dreaded cytokine storm that has often been the reason for Covid deaths.
A December 2020 article in New England Journal of Medicine stated that “cytokine storm and cytokine release syndrome are life-threatening systemic inflammatory syndromes involving elevated levels of circulating cytokines and immune-cell hyperactivation that can be triggered by various therapies, pathogens, cancers, autoimmune conditions, and monogenic disorders”.
ICMR scientists, in a study published in Science Advances in 2021, had documented that BCG vaccine has a role in controlling this hyperimmune response.
They reported that their “results demonstrated that BCG vaccination resulted in diminished plasma levels of types 1, 2, and 17 and other proinflammatory cytokines and type 1 interferons”.
“BCG vaccination also resulted in decreased plasma levels of CC, CXC chemokines, APPs, MMPs, and growth factors. Plasma levels of the aforementioned parameters were significantly lower in vaccinated individuals when compared to unvaccinated control individuals,” they added.
“Thus, our study demonstrates the immunomodulatory properties of BCG vaccination and suggests its potential utility in nonspecific vaccination of Covid-19 by down-modulating pathogenic inflammatory responses.”
(Edited by Nida Fatima Siddiqui)