BCG Vaccine

Type 1 diabetes is caused by the body destroying the cells in the pancreas that produce insulin. This is called autoimmune diseases as the body’s immune system, that it supposed to prevent it from attack by infections, instead attacks itself.

BCG stands for Bacillus Calmette-Guérin. It was developed by two French scientists called Albert Calmette and Camille Guérin. It was introduced in 1921 and has been used extensively to give immunisation against tuberculosis.

BCG has a number of interesting effects on the immune system which mark it out as rather different from other vaccines. The immune system may be important in detecting and destroying early cancer. BCG has been shown to be of value in superficial bladder cancer. There have been a number of small trials of the effect of BCG on various autoimmune diseases including type 1 diabetes.

Trials in mice have used BCG to kill the immune cells that are responsible for destroying the insulin producing cells in the pancreas that cause type 1 diabetes. Studies have shown a permanent cure for about a third of the test subjects. Because it works in experimental mice does not mean that it will work in humans too.

In the UK and many other countries where tuberculosis is not common, children are given BCG vaccination at about 13 years old. In groups at high risk of tuberculosis in the UK and other countries, as well as countries with a high level of the disease, children are given BCG vaccination soon after birth. This provides a natural experiment to see if the vaccine will protect against type 1 diabetes.

A study from Germany looked at children at risk of diabetes because they had a parent with type 1 diabetes. Some had BCG vaccine before 3 months old. Some had it after 3 months old. Some had not had it at all. There was no evidence that the vaccine gave protection against the process that damaged the insulin producing cells that causes type 1 diabetes.

An epidemiological study from Quebec in Canada examined if BCG seemed to protect against a number of diseases, including type 1 diabetes. There was no evidence that it did.

An American review examined all the good quality papers they could find about the effect of manipulating the immune system to protect against type 1 diabetes. This included not just BCG but drugs such as azathioprine that is usually used to prevent rejection of transplants and methotrexate that is used to suppress the immune system to reduce joint damage in rheumatoid arthritis. They also looked at a number of ways of manipulating the immune system. They concluded that such techniques may have some benefit in protecting the insulin producing cells in newly diagnosed type 1 diabetes but it was too early to be sure. More trials are needed not only to test the effectiveness of such interventions but also to assess possible harm from suppressing the immune system.

If BCG does have a part to play in protecting against type 1 diabetes, it is small and clarification of its role is still a long way off.

Dr Tony Woolfson MB BS DM MRCP(UK)
Learn how to master your diabetes.  Visit my website at www.diabetesdietdoctor.com.