Year : 2020 | Volume
: 34 | Issue : 2 | Page : 55--56
Role of Bacille Calmette-Guérin in offering protection against COVID-19
Sharad Bagri, Ankur Garg, Mohan Bandhu Gupta, SN Gaur
Department of Respiratory Medicine, School of Medical Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India
Dr. S N Gaur
Gaur Clinic,130-A, Patparganj Village, Delhi-110091
|How to cite this article:|
Bagri S, Garg A, Gupta MB, Gaur S N. Role of Bacille Calmette-Guérin in offering protection against COVID-19.Indian J Allergy Asthma Immunol 2020;34:55-56
|How to cite this URL:|
Bagri S, Garg A, Gupta MB, Gaur S N. Role of Bacille Calmette-Guérin in offering protection against COVID-19. Indian J Allergy Asthma Immunol [serial online] 2020 [cited 2021 Dec 6 ];34:55-56
Available from: https://www.ijaai.in/text.asp?2020/34/2/55/300924
A number of epidemiological studies have demonstrated a negative association between national Bacille Calmette-Guérin (BCG) vaccination policy and the mortality from coronavirus disease (COVID-19). But, however, the signals of BCG vaccination effect on COVID-19 mortality are influenced by social, economic, and demographic differences between countries along with timing of arrival of pandemic, number of diagnostic tests, and national strategies to control COVID-19.
Efforts for developing vaccines for novel COVID-19 are ongoing, but it is unlikely to be available in the immediate future. In the absence of specific therapy, the researchers are exploring other potential preventive and therapeutic options. Recently, there has been a buzz about the protective effect of BCG vaccine in COVID-19. Based on epidemiological correlations, many unpublished preprints hypothesized that the BCG vaccine may offer protection against COVID-19.
Why Bacille Calmette-Guérin May Work Against Sars-COV2
BCG is a live attenuated vaccine that was developed against tuberculosis at the beginning of the 20th century. Since then, it has been the most used vaccine in the world, with around 130 million children vaccinated every year. Interestingly, however, soon after its introduction in Europe in the 1920s, epidemiological studies reported that BCG vaccination strongly reduced infant mortality, and this could not be explained by a reduction in tuberculosis alone (reviewed previously). Later on, similar studies in other locations, including randomized controlled trials, showed an up to 50% reduction of mortality induced by BCG in young infants. This reduction in childhood mortality by BCG appeared to be due to the protection against unrelated infectious agents and especially respiratory tract infections and neonatal sepsis. Although the authors did not discriminate between bacterial and viral infections in these studies, it is well-known that viral pathogens are the main cause of respiratory tract infections in children. This hypothesis was strengthened by a study in Guinea-Bissau showing that BCG reduced the incidence of respiratory syncytial virus infection. A similar protective effect of BCG on respiratory tract infections was found in older individuals in Indonesia, and a clinical trial performed in Japan demonstrated protection against pneumonia in tuberculin-negative older individuals. Last, a recent study in adolescents in South Africa also reported a 70% reduction of respiratory tract infections by BCG vaccination.
Investigators are now looking to test the hypothesis that heterologous protection engendered by BCG could protect against severe disease from COVID-19. Interestingly, data from a nonpeer-reviewed publication provide some support for this hypothesis. The authors of this article found that parts of the world that do not have a policy of universal BCG vaccination, such as Italy and the USA, have experienced higher mortality associated with COVID-19 than places with long-standing universal BCG vaccination policies, such as South Korea and Japan.
Studies are in progress to determine whether BCG vaccination could protect against COVID-19 infection. Whatever the results of these efforts, that the BCG vaccine continues to spark scientific investigations that shed new light on our understanding of immunological mechanisms over 100 years since its development is remarkable. If the BCG vaccine or another inducer of trained immunity provides nonspecific protection to bridge the gap before a disease-specific vaccine is developed, this would be an important tool in the response to COVID-19 and future pandemics.
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