Moderna Inc. shares are selling off Wednesday, after the Trump administration took aim at the science behind the biotechnology company’s vaccines and said it would cancel some contracts and stop funding mRNA drug development.

The targeting of the vaccine technology once considered revolutionary follows intense criticism by conservatives and anti-vaccine activists.

Health Secretary Robert F Kennedy Jr, a vaccine sceptic, announced he was pulling the funding over claims that "mRNA technology poses more risks than benefits for these respiratory viruses". Doctors and health experts have criticised Kennedy's longstanding questioning of the safety and efficacy of vaccines and his views on health policies.