An experimental vaccine is effective at preventing pneumonia in mice infected with the COVID-19 virus, according to a study.

The vaccine, which is made from a mild virus genetically modified to carry a key gene from the Covid-19 virus, is published in the journal Cell Host and Microbe. "Unlike many of the other vaccines under development, this vaccine is made from a virus that is capable of spreading in a limited fashion inside the human body, which means it is likely to generate a strong immune response," said study author Michael S. Diamond from the Washington University.