The CDC, a $9.2 billion-a-year agency tasked with reviewing life-saving vaccines, monitoring diseases and watching for budding health threats, is without a clear leader.

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.