A top cabinet official is leaving her post in the Mills Administration to take a job at a Washington D.C. think tank and to teach at Harvard.

Jeanne Lambrew, commissioner of the Department of Health and Human Services, will leave at the end of the month, the governor’s office announced Tuesday.

Lambrew was Mills’ first hire as a cabinet member in 2018 and has led the expansion of health care to more than 100,000 people, coordinated the state’s COVID-19 response and worked to increase investments in human services.

“I have worked with my fair share of Health and Human Services Commissioners throughout my career, and I can unequivocally say that Jeanne Lambrew is a once-in-a-generation public servant,” Mill said in a statement.

The largest department in state government, DHHS oversees aging and disability services, behavioral health, child and family services, the health insurance marketplace, Medicaid, welfare programs, licensing and certification, disease control and prevention and two state run psychiatric hospitals.

In recent years, the department has come under fire for its Office of Child and Family Services division following the high-profile deaths of young children who had received services from the department.

In November, the head of the office, Todd Landry, resigned from the post following increasing scrutiny from lawmakers and others.

Last week, the department announced it is joining a national collaborative to improve child safety in Maine. In addition, the department said it has reduced caseworker vacancies by 25% since January, increased pay for child welfare staff, added staff support for administrative tasks and increased funding for children in rural areas.

Lambrew is set to become director of health care reform for The Century Foundation, which conducts research and drives policy change, and to work as an adjunct professor of health policy at the Harvard T.C. Chan School of Public Health, according to the governor’s office.

In a statement, the Maine Hospital Association praised Lambrew for her work during the pandemic and in expanding health care coverage to thousands more Mainers.

“There were many trying times throughout the COVID-19 pandemic, but the Commissioner never wavered in her commitment to getting hospitals the critical support they needed to meet the challenge of caring for our communities, whether it be additional workers, testing supplies, PPE or vaccines,” Steven Michaud, association president, said in a statement.