Current and former IHS clinicians told ProPublica the changes threaten vaccine uptake in Navajo communities and have left medical practitioners who serve this population feeling censored.

“It seems to me that they’re trying to put up barriers,” said Harry Brown, a physician and epidemiologist who left IHS in 2016 and now works for a tribally operated health facility in North Carolina. In a 26-year career with IHS, he said, he had never encountered an effort to stifle public health campaigns or restrict what medical providers said publicly about vaccines.

Aside from Brown, the health care providers who spoke with ProPublica didn’t want their names used, concerned it could endanger their jobs. One physician said the new IHS restrictions on vaccine-related speech factored into her decision to leave the agency this year.

“I can’t keep people safe,” she said in an interview just before she quit. “I don’t have any of the words anymore to say anything I need to say.”