Robert F. Kennedy Jr.’s shock decision to cancel nearly half a billion dollars’ worth of research projects because they’re based on mRNA technology horrified vaccine experts Tuesday, among them President Donald Trump’s own former surgeon general.

Jerome Adams, who served as the nation’s 20th surgeon general during Trump’s first term, warned on social media that the decision will have very real negative consequences.

“I’ve tried to be objective & non-alarmist in response to current HHS actions – but quite frankly this move is going to cost lives,” he wrote. “mRNA technology has uses that go far beyond vaccines… and the vaccine they helped develop in record time is credited with saving millions.”

Adams ended the missive with the “head exploding” emoji.

In another thread, Adams blamed politicized messaging around vaccination during the coronavirus pandemic for leading to a widespread public misunderstanding of what vaccines actually accomplish.