Is There a Rationale for Using Bacillus Calmette-Guerin Vaccine in Coronavirus Infection?

Effect of BCG on Respiratory Complications Caused by COVID-19: A Scoping Review

Introduction

Bacillus Calmette-Guérin (BCG) has been shown to have protective effects against respiratory viruses. We conducted a scoping review of the literature to clarify the available evidence regarding the effect of BCG therapy in preventing respiratory complications of coronavirus disease 2019 (COVID-19).

Methods

We searched PubMed, Embase, CENTRAL, Scopus, and Web of Science for related studies up to October 2022.

Results

In total, 35 publications and trials were included. One animal study, two observational studies, and six finalized trials measured the effect of BCG administration on respiratory complications of COVID-19. The remaining publications included eight unfinished trials, 12 ecological studies, and six observational studies that did not directly measure respiratory complications but assessed overall mortality of the disease and were included as an adjunct to our study. All trials involved vaccinating adults to protect them against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, and measured respiratory symptoms or the need for intensive respiratory support as the primary or secondary aim of the study. One trial that exclusively included at-risk adults between 18 and 60 years old showed a decreased chance of respiratory complications as the secondary outcome of the study. Another trial that exclusively evaluated this effect on the elderly (60 years and older) as the primary aim of the study reported no protective effect against respiratory complications. The remaining literature provided mostly inconclusive evidence.

Conclusion

The majority of the literature on the protective effect of BCG against respiratory complications of COVID-19 is inconclusive.

Does bacille calmette–Guérin vaccination provides protection against COVID-19: A systematic review and meta-analysis

Background:

Lower morbidity and mortality in few geographic locations on the globe suffering with SARS-CoV-2 has been associated with the existing or previously followed long-standing Bacille Calmette–Guérin (BCG) vaccination policy among infants. However, does it hold true that today after years of BCG vaccination, few adults have better prognosis or is it just confounding due to differential disease burden, population density, testing facilities, or improper reporting. The purpose was to evaluate and correlate this effect systematically.

Methods:

Detailed electronic search for randomized controlled trials (RCTs) and observational studies in PubMed, Cochrane Library, and ClinicalTrials.gov for eligible studies was performed.

Results:

One hundred and fourteen studies were yielded on search strategy and 28 observational studies were finally included for analysis. From our results, we can say that BCG vaccination causes a decrease in COVID-19 incidence and mortality. However, these results must be interpreted cautiously as lot of confounding factors were present in included studies, which can affect the outcome.

Conclusion:

The evidence of BCG vaccination for the protection against COVID-19 cannot be ruled out as evidence from many studies support the hypothesis, but the evidence of well-conducted RCTs and observational studies can strengthen the evidence.

Registration Number:

PROSPERO (International Prospective Register of Systematic Reviews) database (CRD42020204466).