Cheap and Commonplace: Making the Case for BCG and γδ T Cells in COVID-19

Alexandra L. Morrison*, Sally Sharpe, Andrew D. White, Mark Bodman-Smith

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Antigen-specific vaccines developed for the COVID-19 pandemic demonstrate a remarkable achievement and are currently being used in high income countries with much success. However, new SARS-CoV-2 variants are threatening this success via mutations that lessen the efficacy of antigen-specific antibodies. One simple approach to assisting with this issue is focusing on strategies that build on the non-specific protection afforded by the innate immune response. The BCG vaccine has been shown to provide broad protection beyond tuberculosis disease, including against respiratory viruses, and ongoing studies are investigating its efficacy as a tool against SARS-CoV-2. Gamma delta (γδ) T cells, particularly the Vδ2 subtype, undergo rapid expansion after BCG vaccination due to MHC-independent mechanisms. Consequently, γδ T cells can produce diverse defenses against virally infected cells, including direct cytotoxicity, death receptor ligands, and pro-inflammatory cytokines. They can also assist in stimulating the adaptive immune system. BCG is affordable, commonplace and non-specific, and therefore could be a useful tool to initiate innate protection against new SARS-CoV-2 variants. However, considerations must also be made to BCG vaccine supply and the prioritization of countries where it is most needed to combat tuberculosis first and foremost.

Original languageEnglish
Article number743924
JournalFrontiers in Immunology
Publication statusPublished - 8 Sep 2021

Bibliographical note

Funding Information: This work was supported by a Public Health England PhD studentship and the Institute for Cancer Vaccines and
Immunotherapy (Registered Charity Number 1080343).

Open Access: This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted,
provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Publisher Copyright: © Copyright © 2021 Morrison, Sharpe, White and Bodman-Smith.

Citation: Morrison, Alexandra L., et al. "Cheap and Commonplace: Making the Case for BCG and γδ T Cells in COVID-19." Frontiers in Immunology (2021): 3612.



  • antiviral
  • Bacille Calmette-Guérin vaccine
  • COVID-19
  • gamma delta T cell
  • innate immunity
  • non-specific immunity
  • trained immunity
  • vaccine


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