The Bacillus Calmette-Guérin vaccine, a century-old tuberculosis vaccine, significantly reduced COVID-19 incidence and provided broad protection against other infectious diseases in patients with type 1 diabetes, according to results from a recent trial.
The recent Phase III randomized, double-blind, placebo-controlled study, published in iScience, was conducted by researchers from Massachusetts General Hospital from April 2021 to November 2022. The study enrolled 141 adults with type 1 diabetes (T1D), randomized in a 2:1 ratio to receive either the multi-dose Tokyo-strain Bacillus Calmette-Guérin (BCG) vaccine or a placebo. Findings showed that the BCG vaccine significantly reduced the incidence of COVID-19 by 43.2% compared to the placebo (p = 0.023) and showed robust protection against all infectious diseases (p < 0.0001).
During the trial, researchers also administered commercial mRNA COVID-19 vaccines to participants. However, they noted that these vaccines did not confer significant protection against COVID-19 in the T1D cohort (p = 0.43). The study period encompassed the dominance of the Beta, Gamma, Delta, and Omicron variants, demonstrating BCG's effectiveness across multiple SARS-CoV-2 strains.
Researchers noted the study builds on previous Phase II trial results, which showed “near total protection” from COVID-19 (92% vs. placebo) early in the pandemic. They excluded individuals with prior BCG vaccinations or tuberculosis exposure to avoid confounding factors related to pre-existing immunity.
The researchers suggested that the BCG vaccine’s broad-spectrum protection is likely due to its ability to induce long-lasting immunological changes. “While mRNA vaccines are a leap forward for most individuals based on alacrity of vaccine production and biological response, the protection is short-term (a matter of months) in the face of viral genetic drift,” they noted. "BCG vaccines appear to offer a platform opportunity but with caveat that benefits may not be manifest for a minimum of 2 years. Nevertheless, BCG offers the prospect of near lifelong protection."
This clinical trial was financially supported by The Iacocca Foundation. No authors disclosed conflicts of interest.
