Despite widespread chatter and the initiation of clinical trials related to the possibility that the Bacille Calmette-Guérin vaccine (BCG) is protective against infection with COVID-19 virus, the World Health Organization (WHO) says there is currently no evidence of that.
The WHO notes that clinical trials addressing this question are underway and that it will evaluate the evidence when it is available.
“In the absence of evidence, WHO does not recommend BCG vaccination for the prevention of COVID-19,” the organization's website states. “WHO continues to recommend neonatal BCG vaccination in countries or settings with a high incidence of tuberculosis.”
The global health group notes the presence of experimental evidence from both animal and human studies that the BCG vaccine has nonspecific effects on the immune system but cautions, “These effects have not been well characterized and their clinical relevance is unknown.”
An updated evidence review in April yielded three preprints (manuscripts posted online before peer review) in which the authors compared the incidence of COVID-19 cases in countries where the BCG vaccine is used with with that in countries where it is not used and observed that countries that routinely used the vaccine in neonates had fewer reported cases of COVID-19 to date. The WHO warns, “Such ecological studies are prone to significant bias from many confounders, including differences in national demographics and disease burden, testing rates for COVID-19 virus infections, and the stage of the pandemic in each country.”
BCG vaccination prevents severe forms of tuberculosis in children, and diversion of local supplies may result in neonates not being vaccinated, resulting in an increase of disease and deaths from tuberculosis, global health officials emphasize.
Baylor College of Medicine in Houston is one of the sites beginning a clinical trial to access the BCG vaccine for its activity against COVID-19. In addition to Baylor College, four other institutions have opened enrollment for the BCG vaccine trial, according to a press release.
BCG vaccination mitigates the rate of other infections, according to Baylor College of Medicine Assistant Professor Andrew DiNardo, MD, and was found to help trigger an immune response against yellow fever and influenza. Dr. DiNardo suggests that the vaccine might lead to 30% to 50% improvement in immune response against a pathogen such as SARS-CoV-2.
The Baylor clinical trial will test the vaccine versus placebo in healthcare workers who treat COVID-19 patients and are at high risk of exposure. Participants will be tracked using a questionnaire on a smartphone every few days over 6 months, according to researchers.
The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.
« Click here to return to Vaccine Update.