Abstract
After a century of controversies on its usefulness in protection against TB, underlying mechanisms of action, and benefits in various groups and geographical areas, the BCG vaccine is yet again a focus of global attention- this time due to the global COVID-19 pandemic caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Recent studies have shown that human CD4+ and CD8+ T-cells primed with a BCG-derived peptide developed high reactivity to its corresponding SARS-CoV-2-derived peptide. Furthermore, BCG vaccine has been shown to substantially increase interferon-gamma (IFN-g) production and its effects on CD4+ T-cells and these non-specific immune responses through adjuvant effect could be harnessed as cross protection against severe forms of COVID-19.The completion of ongoing BGG trials is important as they may shed light on the mechanisms underlying BCG-mediated immunity and could lead to improved efficacy, increased tolerance of treatment, and identification of other ways of combining BCG with other immunotherapies.
Highlights
Recent studies have shown that human CD4+ and CD8+ T-cells primed with a Bacille Calmette-Guérin (BCG)-derived peptide developed high reactivity to its corresponding SARS-CoV-2-derived peptide (Eggenhuizen et al, 2020; Urbán et al, 2020)
The study results suggest that CD4+ and CD8+ T-cells specific for BCG-derived peptides are cross-reactive to SARS-CoV-2-derived peptides
This may explain the epidemiologic observation that BCG vaccination may protect against COVID-19 disease or death by triggering crossreactive SARS-CoV-2-specific T-cell response
Summary
Based on these reports and epidemiological observations, the potential for BCG vaccination to induce (partial) protection against SARSCoV-2 infection and prevent serious disease was deemed plausible and logical in what was a desperate global situation (Escobar et al, 2020; Patella et al, 2020). There are concerns about the lack of any convincing data on the effectiveness of BCG in preventing serious disease due to SARS-CoV-2 infection.
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