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= BCG vaccine = From Wikipedia, the free encyclopedia Jump to navigationJump to search

Bacillus Calmette–Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is partly named after its inventors Albert Calmette and Camille Guérin. In countries where TB or leprosy is common, one dose is recommended in healthy babies as close to the time of birth as possible. In areas where TB is not common, only children at high risk are typically immunized, while suspected cases of TB are individually tested for and treated. Adults who do not have TB and have not been previously immunized but are frequently exposed may be immunized as well. BCG also has some effectiveness against Buruli ulcer infection and other nontuberculous mycobacteria infections. Additionally it is sometimes used as part of the treatment of bladder cancer.

Rates of protection against TB infection vary widely and protection lasts up to twenty years. Among children it prevents about 20% from getting infected and among those who do get infected it protects half from developing disease. The vaccine is given by injection into the skin. There is no evidence that additional doses are beneficial.

Serious side effects are rare. Often there is redness, swelling, and mild pain at the site of injection. A small ulcer may also form with some scarring after healing. Side effects are more common and potentially more severe in those with poor immune function. It is not safe for use during pregnancy. The vaccine was originally developed from Mycobacterium bovis, which is commonly found in cows. While it has been weakened, it is still live.

The BCG vaccine was first used medically in 1921. It is on the World Health Organization's List of Essential Medicines. As of 2004, the vaccine is given to about 100 million children per year globally.

Type 1 diabetes[edit]
There are many animal model studies in non-obese diabetic mice (NOD) that demonstrate the effectiveness of the BCG vaccine in preventing the onset of type 1 diabetes or completely reversing this autoimmune disease. This effect is thought to be due to an immunomodulation response that blocks β-cell destruction in the pancreas and the resulting insulitis in mice. Human studies have not been able to consistently and confidently reproduce the same extensive benefits that have been found in NOD mice. The focus of human studies has shifted towards evaluating the glycated hemoglobin (HbA1C) in type 1 diabetic patients to observe improvement. The mechanism of action that is thought to decrease the HbA1C is due to a shift in cellular metabolism after BCG vaccine administration. An increase in aerobic glycolysis is observed with a reduction in oxidative phosphorylation leading to accelerated glucose utilization and long-term decrease in HbA1C.

A 2020 systematic review and meta-analysis of studies researching the possible benefits of the BCG vaccine on the clinical improvement of HbA1C in type 1 diabetes was conducted. This review determined that there is no evidence of significant benefit to giving the BCG vaccine in type 1 diabetics. The study noticed a tendency for the HbA1C to improve in the BCG vaccine treatment groups, however, it was not statistically significant. Another outcome measured was the fasting C-peptide levels, but no significant difference was found between the BCG vaccine groups and the placebo groups. The review concluded that these results need to be interpreted carefully due to the small sample size and limited research in this field. Further research needs to be done to fully understand the mechanism of action of the BCG vaccine as well as its potential uses in type 1 diabetes.

COVID-19[edit]
Use of the BCG vaccine may provide protection against COVID‑19. However, epidemiologic observations in this respect are ambiguous. The WHO does not recommend its use for prevention as of 12 January 2021.

As of January 2021, twenty BCG trials are in various clinical stages.