100 Year Old Vaccine Protects People From Infectious Diseases

New research published by investigators at Massachusetts General Hospital (MGH) shows that the 100-year-old Bacillus Calmette-Guérin (BCG) vaccine, originally developed to prevent tuberculosis, protects individuals with type 1 diabetes from infectious diseases.

Two back-to-back randomized double-blinded placebo-controlled trials found that the BCG vaccine provided continuous protection for nearly the entire pandemic in the U.S., regardless of the SARS-CoV-2 variant.

The MGH Phase II and Phase III clinical trials testing BCG differed from other BCG trials in important ways.

Instead of receiving one dose of BCG, participants received five or six doses of a particularly potent strain of BCG vaccine.

“Individuals with type 1 diabetes are highly susceptible to infectious diseases and had worse outcomes when they were infected with the SARS-CoV-2 virus,” said senior author Denise Faustman, MD, PhD, director of the Immunobiology Laboratory at MGH and an Associate Professor of Medicine at Harvard Medical School, in a press release.

“....we’ve shown that BCG can protect type 1 diabetics from COVID-19 and other infectious diseases.”  

The 18-month Phase III trial, published in iScience, was conducted when the highly transmissible Omicron variant was circulating.

A 15-month Phase II trial was conducted early in the pandemic; the results of that trial were published in Cell Reports Medicine.

During the COVID-19 pandemic, several international trials tested whether BCG, given as a single shot or booster to previously BCG-vaccinated adults, protected them from infection and COVID-19.

However, results from these COVID-19 booster trials were mixed in people previously vaccinated with BCG. Five randomized trials showed efficacy, and seven trials showed no benefit. 

 “Our study showed that the BCG vaccine neither increased the efficacy of the COVID-19 vaccine nor was it harmful to those who received the COVID-19 vaccine,” said Faustman.

The U.S. participants were followed for 36 months instead of weeks or months.

“We know that in people who are naïve to BCG vaccine, the off-target effects can take at least two years to achieve full protection,” said Faustman. “Giving multiple doses of the vaccine may speed up that process.”

The MGH trials enrolled 141 participants with type 1 diabetes; 93 people in the treatment group received five or six doses of BCG vaccine, and the 48 individuals in the placebo group received sham vaccine and were followed for 36 months to capture diverse COVID-19 genetic variants and many infectious disease exposures.

During the earlier Phase II trial (January 2020 to April 2021), when the virus was more lethal but less transmissible, the BCG vaccine’s efficacy was 92%, comparable to the efficacy of COVID-19 vaccines in healthy adults.

Over 34 months of the pandemic, the BCG vaccine had a significant efficacy of 54.3%.

The investigators also found that the BCG-treated participants had lower viral, bacterial, and fungal infection rates.

This research expanded the extensive global clinical trial database, showing that BCG administered to newborns works as a platform for all infectious diseases, maybe for decades.

In the U.S., BCG vaccinations have been an effective treatment for bladder cancer for several years.

Massachusetts General Hospital, founded in 1811, is the original and largest teaching hospital of Harvard Medical School. This research was supported by The Iacocca Foundation, Boston, MASS. No conflicts of interest were disclosed.