BCG: Can a vaccine from 1921 save lives from Covid-19?
BCG strikes again
The vaccine was designed to stop tuberculosis, but there is some evidence it can protect against other infections as well.
Around 1,000 people will take part in the trial at the University of Exeter.
But while millions of people in the UK will have had the BCG jab as a child, it is thought they would need to be vaccinated again to benefit.
Vaccines are designed to train the immune system in a highly targeted way that leaves lasting protection against one particular infection.
But this process also causes wide-spread changes in the immune system. This seems to heighten the response to other infections and scientists hope it may even give our bodies an advantage against coronavirus.
Previous clinical trials have shown the BCG jab reduced deaths by 38% in newborns in Guinea-Bissau, mostly by reducing cases of pneumonia and sepsis.
Studies in South Africa linked the vaccine to a 73% reduction in infections in the nose, throat and lungs; experiments in the Netherlands showed BCG reduced the amount of yellow fever virus in the body.
"This could be of major importance globally," Prof John Campbell, of the University of Exeter Medical School, told the BBC.
"Whilst we don't think it [the protection] will be specific to Covid, it has the potential to buy several years of time for the Covid vaccines to come through and perhaps other treatments to be developed."
The UK trial is part of the international Brace-study, which is also taking place in Australia, the Netherlands, Spain and Brazil, recruiting 10,000 people in total.
It will focus on health and care workers, as they are more likely to be exposed to coronavirus, so researchers will know more quickly if the vaccine is effective.