Tuberculosis vaccine BCG: the magical effect of the old vaccine in the fight against the COVID-19 pandemic

Abstract

Bacillus Calmette-Guérin (BCG) is a live attenuated M. bovis vaccine that was developed about 100 years ago by Albert Calmette and Camille Guérin. Many countries have been using the vaccine for decades against tuberculosis (TB). The World Health Organization (WHO) recommends a single dose of BCG for infants in TB endemic as well as leprosy high risk countries, and globally almost 130 million infants are vaccinated yearly. The role of BCG is well known in reducing neonatal and childhood death rates. Epidemiological and retrospective cross-sectional studies demonstrated that the BCG vaccination protects the children against respiratory tract infections and lowers the risk of malaria in children. In addition, BCG enhances IFN-γ and IL-10 levels, thus providing immunity against respiratory tract infection even in elderly people. The BCG is also known to provide nonspecific innate immunity against viruses and parasites, through an innate immune mechanism termed ‘trained immunity’ and is defined as the immunological recall of the innate immune system by epigenetic reprogramming. Based on these studies it is suggested that the BCG has the potential to act as a protective agent against COVID-19. Further proven safety records of BCG in humans, its adjuvant activity and low-cost manufacturing make it an attractive option to stop the pandemic and reduce the COVID-19 related mortality. In this review we discuss the heterologous effects of BCG, induction of trained immunity and its implication in development of a potential vaccine against COVID-19 pandemic.

Differential Diagnosis of Latent Tuberculosis Infection and Active Tuberculosis: A Key to a Successful Tuberculosis Control Strategy

“…It has been reported that 5-10% of patients with LTBI will progress to aTB during their lifetime (Hauck et al, 2009;Chee et al, 2018;WHO, 2018). However, the risk is higher in immunocompromised individuals, such as in people living with human immunodeficiency virus (HIV), people with diabetes, people with coronavirus disease, infants, and young children (aged < 5 years) (Chee et al, 2018;Gong and Wu, 2020;WHO, 2020;Aspatwar et al, 2021). In 2019, the number of new TB cases in countries with high TB burdens accounted for 86.9% of the global number of new TB cases (WHO, 2020).…”

COVID-19 and Beyond: Exploring Public Health Benefits from Non-Specific Effects of BCG Vaccination

“…Literature specifically addressing the effectiveness of BCG at improving morbidity and mortality resulting from COVID-19 disease remains varied and sometimes inconsistent [ 75 ]. This area of investigation is rapidly emerging and has garnered a great deal of interest [ 76 , 77 , 78 ]. Here, we review studies specifically investigating the effects of BCG vaccination on COVID-19 spread, morbidity, and mortality, excluding papers that have not yet been peer reviewed ( Table 2 ).…”

mRNA SARS-CoV2 Specific and Childhood Vaccines against Covid-19 Pandemic

“…Besides, recovery rates from SARS-CoV2 infection are higher in those countries as well. Therefore, BCG vaccination seems a promising approach to overcome SARS-CoV2 pandemic with its benign nature to human health [104]. In silico studies, based on homology, revealed that BCG vaccination can trigger production of cross-reactive T cells against SARS-CoV2 [105] along with enhanced innate immunity [106].…”

“…Cross-reactive dendritic cells (i.e. inf-cDC2s) that priming type I INF dependent [114] CD4 + and CD8 + T cells activation [108]; Downregulation of proinflammatory cytokine production [127]; various antiviral cytokine production, enhanced IFN-γ production and associated TH1 cells differentiation [104].…”