BCG is first and foremost the world's most common tuberculosis vaccine, and was first used in humans all the way back in 1921. Made from a weakened strain of live bovine tuberculosis bacteria, it's been show to be up to 80 per cent effective in preventing TB for a duration of 15 years, depending on geographical location. That's pretty impressive, which is why - US aside - it's shoved into many a childhood arm around the world. But that's just the beginning.
Jumping from TB to cancer is quite a leap, but it's one BCG has made time and again. As far back as 1979, a clinical trial declared that "BCG is beneficial in the treatment of lung cancer". Then, in 1991, a study published in the new England Journal of Medicine suggested that the BCG vaccine offered strong protection against the recurrence of bladder cancer.
There followed a 1994 trial which provided evidence that BCG increased survival time and reduced risk of recurrence in those suffering from malignant melanoma; reports that it was beneficial in the treatment of colorectal cancer; and, most recently, concrete examples of its beneficial effects in bladder cancer treatment.
TB, dead. Four disparate types of cancer kept in check. That alone would make for a pretty impressive scorecard.
But wait, there's more
But BCG has plenty more up its sleeve. Take multiple sclerosis, a disease in which the fatty sheaths around axons in the brain become damaged, in turn leading to scarring and, over time, cognitive disability. In 1999, it was demonstrated that BCG reduced the incidence of MS symptoms.
In a later study, it was shown that this effect was likely due to the fact the vaccineattenuated the scarring of nerve cells by up to 50 percent - an effect that was observed on MRI scans. While it's not commonly used as a treatment, it was deemed a safe and sensible use of the vaccine in the journal Neurology.
The list keeps going. A 2006 paper in the Lancet explained how BCG has a protective effect on leprosy, while another pointed out that it delayed the onset of Buruli ulcers - nasty growths beneath the surface of the skin. There are also a host of animal experiments which promise even more positive news: in particular, a mouse model of Parkinson's disease has shown that BCG provides a mild neuroprotective effect, and it's hoped it can be replicated in humans.
Not bad for a 90-year old treatment.
Old drug, new tricks
She demonstrated that the vaccine helped mice to produce a protein which kills off T-cells, which are responsible for type 1 diabetes. With bated breath, the scientific community waited while the same experiments were replicated in humans. What was at stake? A positive finding could mean that diabetes patients no longer had to inject themselves with insulin.
Four years later, Fausmtan and her colleagues have published results from a very small-scale trial in PLoS One. Their work is limited and caveat-laden - the study looked at three patients for just 20 weeks - but the researchers observed the same protein production and T-cell death as they saw in mice. While it's not quite time for diabetes sufferers to pop the champagne corks and stop injecting insulin just yet, it's certainly a major finding that promises a great deal.
Perplexingly, we don't even really know quite what makes BCG so successful. There are hypotheses that suggest that it activates a protein called the "tumour necrosis factor-alpha" - and the diabetes study lends some weight to that idea - but the research community isn't 100 per cent sure yet. Put simply, though it seems to be helpful across many conditions, we don't yet know exactly why.
Ignore at your own risk
Given the success of BCG against so many disease, you might wonder why it's not more common. It's certainly not unsafe: it's one of the most widely used vaccines in the world, and has few adverse effects other than a little scarring where the injection is given. It's certainly not prohibitively expensive, either, as it's used throughout vast swathes of Asia and South America.
Perhaps more likely is that the US — usually the pioneer in cutting-edge treatments — has never really embraced BCG. Instead, it's always shunned the vaccine as a TB preventative, instead preferring to opt for programs of detection and treatment of latent tuberculosis. In turn, BCG is less commonplace in the US: medical professionals aren't as generally aware of it as in other parts of the world and, as a result, it sometimes goes overlooked.
Given what a panacea it's proven to be, though? Perhaps it's time that changed.
Image by Andres Rueda under Creative Commons license