The resignation, first reported by The Associated Press and confirmed by CBS News, comes just a week after health secretary and anti-vaccine advocate Robert F. Kennedy Jr. unilaterally revoked and altered some of the CDC’s recommendations for COVID-19 vaccines, restricting access to children and pregnant people. The resignation also comes three weeks before CDC’s experts and advisors are scheduled to meet to publicly evaluate data and discuss the recommendations for this season—a long-established process that was disrupted by Kennedy’s announcement.

The departing CDC official, Lakshmi Panagiotakopoulos, a pediatric infectious disease expert, was a co-leader of a working group on COVID-19 vaccines who advised experts on the CDC’s Advisory Committee on Immunization Practices (ACIP). She informed her ACIP colleagues of her resignation in an email on Tuesday.

“My career in public health and vaccinology started with a deep-seated desire to help the most vulnerable members of our population, and that is not something I am able to continue doing in this role,” Panagiotakopoulos wrote.