UnitedHealth Group is promoting former GlaxoSmithKline leader Sir Andrew Witty to become the health insurance provider’s next CEO immediately.

The company said Thursday that current CEO David Wichmann will retire, more than three years after being promoted from his role as company president.

The 56-year-old Witty had served as CEO of UnitedHealth’s Optum segment and then became president of the parent company in November 2019. Before that, he ran the British drugmaker GlaxoSmithKline for several years.

Witty took a leave of absence last spring from UnitedHealth to help lead a World Health Organization push to accelerate COVID-19 vaccine development. He returned at the end of the year.

UnitedHealth runs UnitedHealthcare, a health insurance business that covers more than 48 million people mostly in the United States. It also has been growing the Optum segment Witty ran. That business operates one of the nation’s largest pharmacy benefit managers as well as a growing number of clinics and urgent care and surgery centers.

UnitedHealth also named UnitedHealthcare leader Dirk McMahon its president and chief operating officer.

The leadership changes come a few weeks after UnitedHealth reported fourth-quarter earnings that easily beat expectations on Wall Street. The company earned $15.4 billion last year after bringing in more than $200 billion in revenue.

Wichmann, 59, joined UnitedHealth in 1998 and became its CEO in September 2017.

Shares of Minnetonka, Minnesota-based UnitedHealth Group Inc. slipped 2% to $330.41 while broader markets climbed in Thursday afternoon trading.