Around a dozen research institutions in the U.S., Europe and Australia are already investigating the potential for self-spreading vaccines in the wake of the coronavirus pandemic.

Most of the research is on animal-to-animal or animal-to-human spread, with human research so far focusing on whether the idea is safe in principle.

The research is being subsidised by high-profile funding organisations, including the U.S. National Institutes of Health (the country’s main medical research agency).

To make a transmissible vaccine requires finding ways to package the virus or bacteria so it can be easily transmitted from one person to another, but without causing serious illness.

Two options are now the focus of research. The first is to engineer in the laboratory a very mild form of the virus you want to protect against.