China's vaccine developers stuck with unused mRNA COVID-19 shots and idle manufacturing plants are pursuing new targets for the novel messenger RNA technology, but they face a tough path, crimped by a lack of revenue.

Three Chinese companies — Walvax Biotechnology, CSPC Pharmaceutical Group and Stemirna Therapeutics — came up with mRNA vaccines that won limited emergency approvals in Asia.

However, Walvax and CSPC are not currently manufacturing three of their China market shots, a China health official said.