A vaccine developed a century ago to prevent tuberculosis has now been found to prevent individuals with type 1 diabetes from catching infectious diseases such as COVID-19.

New studies from the Massachusetts General Hospital (MGH) have discovered that the Bacillus Calmette-Guérin (BCG) vaccine provided people with type 1 diabetes in the US with protection from the coronavirus during the pandemic.

First author Dr Denise Faustman said: “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.

“Published data from other investigators show mRNA COVID-19 vaccines are not very effective in this group of vulnerable people. But we’ve shown that BCG can protect people with type 1 diabetes from COVID-19 and other infectious diseases.”

These clinical trials saw 93 participants being given five or six doses of a particularly potent strain of the BCG vaccine for 36 months.

Meanwhile, the remaining 48 individuals taking part in the study were given a placebo for the same amount of time.

Dr Faustman said: “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. Giving multiple doses of the vaccine may speed up that process.”

Until recently, adults in the US had never received BCG vaccines, according to the researchers involved in the clinical trials.

Dr Faustman added: “The Phase II and Phase III trials conducted at MGH were unique in that they were the only COVID trials in the world in which the study population had never received a BCG vaccine and was never exposed to tuberculosis.

“Trials conducted in countries where participants had previously received BCG vaccine as newborns or who had previous exposure to tuberculosis may have obscured any benefit from a BCG booster.”

According to the results, the BCG vaccine was as effective as the Pfizer and Moderna vaccines for protecting people from COVID-19.

The results have shown that the efficacy of the BCG vaccine throughout the entire trial was 54.3%.

Those who received the BCG vaccine also had lower rates of fungal, viral and bacterial infections, the study has reported.

Dr Faustman noted: “The BCG vaccine offers the prospect of near-lifelong protection against every variant of COVID-19, the flu, respiratory syncytial virus and other infectious diseases.”

The two studies are available in iScience and Cell Reports Medicine.

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