The first indication of the broad infectious disease–protective abilities of the bacillus Calmette-Guérin (BCG) vaccine came 100 years ago when Albert Calmette, the vaccine’s coinventor, noted a fourfold decline in child mortality (unrelated to tuberculosis) in vaccinated children, presumably from broad infectious disease protection. These protective effects also appear when adolescents are revaccinated with the BCG vaccine after the typical newborn dose. The BCG vaccine may also protect humans from immune diseases, such as type 1 diabetes (T1D) and multiple sclerosis.
A recent study was published in Cell Reports Medicine and was led by researchers from the Massachusetts General Hospital in Boston to demonstrate the protective potential of multiple doses of the BCG vaccine against COVID-19 and other infectious diseases.
Denise Faustman, MD, PhD, director of the immunobiology laboratory at Massachusetts General Hospital and lead author of the study, and colleagues explored the use of the old and inexpensive BCG vaccine—which was originally developed to prevent tuberculosis—to now fight COVID-19. The authors of the study promoted its safety as one that has had nearly four billion people already vaccinated with what they call their “platform vaccine.”
“Unlike the antigen-specific vaccines currently in use to prevent COVID-19, BCG’s mechanism of action is not limited to a specific virus or infection,” stated Dr. Faustman. The researchers focused their work on high-risk populations, including people with diabetes, and reaffirmed the importance of their work, stating, “Multiple studies have shown that adults with type 1 diabetes who are diagnosed with COVID-19 are at increased risk of severe illness.”
The team conducted a 15-month randomized, double-blinded, placebo-controlled trial to determine the efficacy and safety of the multidose BCG vaccine. The study participants had been previously enrolled in a clinical trial evaluating the effectiveness of the BCG vaccine for the treatment of longstanding T1D and received multiple BCG doses prior to the beginning of the COVID-19 pandemic, which was recognized in early 2020.
The study cohort included 144 individuals with diabetes who were then randomized with one group of 96 subjects receiving the BCG vaccine and the remaining 48 subjects receiving a placebo. The team reported efficacy in 92% of the subjects, with only 1% of the BCG-treated individuals meeting criteria for COVID-19 infection, whereas the placebo group had a 12.5% infection rate. Those who tested positive in the BCG-treated group also were reported to have less severe symptoms, and there were no adverse events or dropouts reported in the active treatment arm.
The authors concluded, “This data set is unique and exciting because the patients were all vaccinated with multiple doses of BCG prior to the onset of the epidemic. Prior to the trial they had no known exposure to tuberculosis or prior BCG vaccination. This eliminates the major confounding factors that have limited other trials.”
The researchers reported that three doses of BCG administered prior to the start of the pandemic prevented infection and limited severe symptoms from COVID-19 and other infectious diseases.
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