Interpreting the Results of Trials of BCG Vaccination for Protection Against COVID-19

Christie C A Noble; Nicole L Messina; Laure F Pittet; Nigel Curtis

doi:10.1093/infdis/jiad316

Interpreting the Results of Trials of BCG Vaccination for Protection Against COVID-19

J Infect Dis. 2023 Nov 11;228(10):1467-1478. doi: 10.1093/infdis/jiad316.

Authors

Christie C A Noble^{1

2}, Nicole L Messina^{1

2}, Laure F Pittet^{1

2

3}, Nigel Curtis^{1

2

4}

Affiliations

¹ Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia.
² Infectious Diseases Research Group, Murdoch Children's Research Institute, Parkville, Victoria, Australia.
³ Paediatric Infectious Diseases Unit, Faculty of Medicine, Geneva University Hospitals, Geneva, Switzerland.
⁴ Infectious Diseases, The Royal Children's Hospital Melbourne, Parkville, Victoria, Australia.

Abstract

BCG vaccination has beneficial off-target ("nonspecific") effects on nonmycobacterial infections. On this premise, trials set out to investigate whether BCG provides off-target protection against coronavirus disease 2019 (COVID-19). A literature search identified 11 randomized "BCG COVID-19" trials, with conflicting results. These trials and the differences in their study design are discussed using the PICOT (participants, intervention, control, outcome, and timing) framework to highlight the factors that likely explain their inconsistent findings. These include participant age, sex and comorbid conditions, BCG vaccination strain and dose, outcome measure and duration of follow-up. Understanding how to control these factors to best exploit BCG's off-target effects will be important in designing future trials and intervention strategies.

Keywords: BCG vaccination; COVID-19; SARS-CoV-2; off-target effects.

Publication types

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

MeSH terms

BCG Vaccine
COVID-19* / prevention & control
Humans
Randomized Controlled Trials as Topic
Vaccination

Substances

BCG Vaccine