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

Wenping Gong, Ashok Aspatwar, Shuyong Wang, Seppo Parkkila, Xueqiong Wu

Research output: Contribution to journalReview Articlepeer-review


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 (, Web of Science (, Embase (, and CNKI ( 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.

Original languageEnglish
Pages (from-to)857-880
Issue number7
Early online dateJun 2021
Publication statusPublished - 2021
Publication typeA2 Review article in a scientific journal


  • Bacille Calmette-Guérin (BCG) vaccine
  • clinical trials
  • COVID-19 pandemic
  • SARS-COV-2
  • trained immunity

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Immunology
  • Molecular Medicine
  • Pharmacology
  • Drug Discovery


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