BCG, a live vaccine for tuberculosis developed in 1900, has been shown to significantly reduce mortality from other diseases. Including other infectious diseases and immune-related diseases like Type 1 diabetes, cancer and Alzheimer’s disease. The effect is thought to be related to epigenetic changes on the level of DNA affecting the innate immune system.
The results are amazing. But the vaccine has been off-patent for decades so no pharmaceutical companies are interested in investigating it. A dose costs 6 cents. BCG given at birth to children from Guinea-Bissau with low birth weight reduced all-cause mortality in these children by about 40 percent in the first year of life. The reduction in mortality was the result of fewer cases of non-TB infections, which the vaccine protected against in an undetermined way.
Researchers are trying to develop fancy-schmantzy alternatives that can be patented (such as parts of the TB bacillus attached to nanoparticles). Obviously, these would be far more expensive even if they aren’t more effective than the old BCG vaccine.
Studies show that BCG vaccination can help older people with weakened immune systems. It doesn’t have an effect in healthy adults.