COVID-19 pandemic: SARS-CoV-2 specific vaccines and challenges, protection via BCG trained immunity, and clinical trials

Expert Rev Vaccines. 2021 Jul;20(7):857-880. doi: 10.1080/14760584.2021.1938550. Epub 2021 Jun 15.

Abstract

Introduction: The coronavirus disease 2019 (COVID-19) pandemic continues to spread worldwide and vaccination remains the most effective approach to control COVID-19. Currently, at least ten COVID-19 vaccines have been authorized under emergency authorization. However, these vaccines still face many challenges.Areas covered: This study reviews the concept and mechanisms of trained immunity induced by the Bacille Calmette Guérin (BCG) vaccine and identifies questions that should be answered before the BCG vaccine could be used to combat COVID-19 pandemic. Moreover, we present for the first time the details of current BCG vaccine clinical trials, which are underway in various countries, to assess its effectiveness in combating the COVID-19 pandemic. Finally, we discuss the challenges of COVID-19 vaccines and opportunities for the BCG vaccine. The literature was found by searching the PubMed (https://pubmed.ncbi.nlm.nih.gov/), Web of Science (www.webofknowledge.com), Embase (https://www.embase.com), and CNKI (https://www.cnki.net/) databases. The date was set as the default parameter for each database.Expert opinion: The advantages of the BCG vaccine can compensate for the shortcomings of other COVID-19 vaccines. If the efficacy of the BCG vaccine against COVID-19 is confirmed by these clinical trials, the BCG vaccine may be essential to resolve the challenges faced by COVID-19 vaccines.

Keywords: Bacille Calmette-Guérin (BCG) vaccine; COVID-19 pandemic; SARS-COV-2; clinical trials; trained immunity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adjuvants, Immunologic / administration & dosage
  • BCG Vaccine / administration & dosage
  • BCG Vaccine / immunology*
  • COVID-19 / immunology*
  • COVID-19 / prevention & control*
  • COVID-19 Vaccines / administration & dosage
  • COVID-19 Vaccines / immunology*
  • Clinical Trials as Topic / methods*
  • Humans
  • Immunity, Innate / drug effects
  • Immunity, Innate / immunology*
  • Pandemics

Substances

  • Adjuvants, Immunologic
  • BCG Vaccine
  • COVID-19 Vaccines

Grants and funding

This work was funded by the National Natural Science Foundation of China (Grant No: 81801643); Beijing Municipal Science & Technology Commission (Grant No: 19L2152); Chinese PLA General Hospital (Grant No: QNC19047); Finnish Cultural Foundation; Tampere Tuberculosis Foundation; Jane & Aatos Erkko Foundation; Finnish Foundation for Cardiovascular Research; and the Academy of Finland.