A top coronavirus vaccine adviser at the Centers for Disease Control and Prevention has resigned, citing concerns that she could no longer help vulnerable people after federal health officials rescinded long-standing recommendations to immunize children and pregnant women.

A medical officer at the US Centers for Disease Control and Prevention who was working on the committee that was weighing changes to the agency’s Covid-19 vaccine recommendations resigned on Friday, the same day officials the US Department of Health and Human Services announced they had removed the CDC recommendation for pregnant women and healthy children to get Covid-19 vaccines.