Could the BCG vaccine really ‘reverse’ Type 1 diabetes? – by Lucy Trelfa

Recently, Type 1 diabetes hit the headlines with the media reporting that the ‘BCG vaccine can reverse Type 1 diabetes to almost undetectable levels’. Our research communications officer Lucy Trelfa takes a look behind the headlines.

Type 1 diabetes occurs when the body’s immune system mistakenly attacks and destroys insulin-producing cells in the pancreas. Scientists are searching for treatments to stop this immune attack in the hope that they can develop a ‘vaccine’ to prevent or slow Type 1 diabetes. While we’re making great progress, this area of research is still in its early days. So it’s understandable that the news of a pre-existing vaccine ‘reversing’ Type 1 diabetes is getting people excited.

Sounds like the news people with Type 1 diabetes have been waiting for. But what’s the science behind the headline?

A brief history of the BCG

The BCG vaccine is one of the world’s oldest and is used to protect people against tuberculosis. It’s safe, good at its job and cheap to produce.
As well as protecting against tuberculosis, the BCG vaccine is already used to treat some bladder cancers and holds promise for other conditions, like food allergies and multiple sclerosis. So the past decade has seen a rise in clinical trials testing its effects.

One of these, led by a group of researchers in Massachusetts, is exploring the potential of the vaccine to treat Type 1 diabetes and recent results hit the headlines.

What the headlines said

Several national newspapers covered the story: “BCG vaccine can reverse Type 1 diabetes to almost undetectable levels, eight year study shows”, reporting that “just two injections of BCG could virtually cure the condition for many years at a time.”

Whilst the suggestion of a ‘cure’ got everyone talking, we delved deeper into the science of the story to find out what this could really mean for people with Type 1 diabetes.

What the research paper said

The research team wanted to test if there are any long-term health benefits for people with Type 1 diabetes from having two doses of the BCG vaccine. The main study included three people living with Type 1 diabetes who received the BCG vaccine, compared to three people living with Type 1 diabetes who received a placebo. The researchers followed up all six participants after eight years.

They assessed the levels of HbA1c in the participants’ blood, which gives a long term measurement of blood glucose. At the end of the eight years, the HbA1c of the BCG vaccine group was 6.65% compared to 7.22% of the placebo group. This means the group given the BCG vaccine had a 0.57% improvement in their long term blood glucose, compared to the group given the placebo.

However, this slightly improved blood glucose control was achieved without any increase in the amount of insulin the participants were making, which would have been expected if the insulin-producing cells were now working.

It’s also unclear whether the participants were randomly selected to receive the BCG or placebo, or whether both the researchers and participants knew which treatment they were getting. These factors are really important to avoid misleading results in clinical trials.

The take home message

While this study was reported as being positive, it only involved three people testing the BCG vaccine and three controls, so at this stage we are unable to apply these results to everyone with Type 1 diabetes. It is also possible that the difference in their blood glucose control could be nothing to do with the vaccine, and instead down to normal fluctuations, or better self-management.

Taken together, it’s difficult to draw any conclusions from this research about the effects of the BCG vaccination for the millions of people living with Type 1 diabetes.

Professor Andrew Hattersley from the University of Exeter Medical School said “This study reports to offer hope for patients with Type 1 diabetes but as they have only studied 3 patients; sadly it is much more hype rather than hope. At best the situation with the BCG vaccine is at present ‘not known.’”

What this means for people with Type 1 diabetes

We want to find effective treatments for Type 1 diabetes. Therapies that act on the immune system hold potential for treating Type 1 diabetes in the future, and a vaccine could be part of that.

The main finding from the research paper that grabbed the media’s attention was a ‘long term and stable blood sugar reduction with BCG vaccinations’. This is true, but only in 3 people and it may not be related to the vaccination.

So it’s worth remembering a few key points:

  • This study was performed in very small numbers of people.
  • The improvement in blood glucose control was moderate, and we can’t say for sure that this was due to the BCG vaccine.
  • All people with Type 1 diabetes who took part in the trial continued their insulin therapy and did not make their own insulin, so we can’t say at this stage that being vaccinated with the BCG ‘reverses’ Type 1 diabetes. At best, the results imply it could marginally improve blood glucose control.

You can read the entire research paper on the Nature website, and access the supplementary data here.

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