One compares Kennedy being considered to “having somebody who doesn’t believe in gravity being the head of NASA.”

The news prompted a sell-off across the industry. In the US, shares in Pfizer and Moderna sank more than 5% in early trading, while UK-listed firms AstraZeneca and GSK dropped 2% or more. Russ Mould, investment director at AJ Bell, said the pick had “spooked” shareholders, despite questions about how the new administration might pursue its threats.

Vaccine stocks have struggled since RFK Jr.'s appointment to health secretary, with Moderna and Pfizer seeing the deepest losses.