Could a common vaccine used for decades to protect against tuberculosis help shield health workers from Covid-19?
While developing a specific immunisation against the coronavirus sweeping the planet will likely take many months, researchers are studying the potential benefits of the BCG shot, which many people around the world receive as children.
Laboratories and pharmaceutical firms are racing to find medicines to tackle Covid-19, which has infected more than a million people, killed at least 50,000 and for which there is currently no known treatment, vaccine or cure.
"We have known for decades that BCG has non-specific beneficial effects", in that it protects against diseases other than the one for which it was created, Camille Locht, of the French public health research institute Inserm, told AFP.
Children vaccinated with BCG suffer less from other respiratory illnesses, it is used to treat certain bladder cancers and it could protect against asthma and autoimmune diseases such as type 1 diabetes.
Researchers want to test whether the tuberculosis vaccine could have a similar effect against the new coronavirus, either by reducing the risk of being infected, or by limiting the severity of the symptoms.
In France, where the BCG vaccine was compulsory until 2007, "most of the study participants will have already had a first vaccination", but the protective effect of this decreases over time, said Locht.
The BCG vaccine does not directly protect medics against the coronavirus, but provides a boost to the immune system which may lead to improved protection and a milder infection.
In the case of Covid-19, in addition to infection by the virus itself, some patients have also suffered excessive immune responses, with the uncontrolled production of pro-inflammatory proteins, cytokines.
However, researchers in Spain, instead of using the BCG, would like to try a new tuberculosis vaccine developed by the biotech firm Biofabri.
In Germany, the Max Planck Institute for Infectious Biology is also preparing a trial with a genetically-modified vaccine candidate, developed by the Serum Institute of India.