The officer, Dr. Lakshmi Panagiotakopoulos, a pediatrician, was the CDC co-lead of the group of independent vaccine advisers that had spent months reviewing evidence for annual Covid-19 shots for Americans. They were drafting potential changes to narrow the agency’s recommendation for healthy children and adults under age 65, and had planned to vote on the changes at the group’s next meeting later this month.

“I am writing to let you know that on Friday of last week, I made the decision to end my time as co-lead of the Covid-19 work group, and after 12 years, I will be leaving the CDC,” Panagiotakopoulos wrote in an email to ACIP members that was obtained by CNN.“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.”

Last week, HHS Secretary Robert F. Kennedy Jr. announced on social media that his agency was removing the CDC recommendation for the Covid-19 vaccines for healthy children and pregnant women.

The decision contradicts available medical evidence for pregnant women, who are at higher risk of severe illness from Covid-19 infections, and it usurped the authority of the CDC group, the Advisory Committee on Immunization Practices, or ACIP.

Healthy children can still get Covid-19 vaccines after consulting with a health care provider, a recommendation known as shared decision making. The CDC recommendation for people who are pregnant to get an updated Covid-19 vaccine has been removed from the schedule. The move may make Covid-19 vaccines harder to get and more expensive for those who want them.