Head of top US public health agency resigns

Rochelle Walensky, who was a key figure in the Biden administration's response to Covid-19, did not give a direct reason for her departure, but suggested that the easing of the coronavirus pandemic had brought her tenure at the CDC to a natural endpoint.

"The end of the Covid-19 public health emergency marks a tremendous transition for our country, for public health, and in my tenure as CDC Director," the 54-year-old said in a letter to President Joe Biden which was released to the public.

She said she had taken on the role some two years ago with the goal of "leaving behind the dark days of the pandemic."

Under Walensky the CDC led an unprecedented vaccination campaign as Biden's administration tried to steer the nation out of the pandemic.

She appeared regularly on television to relay prevention messages to Americans and explain the latest measures.

"I have never been prouder of anything I have done in my professional career," Walensky wrote of her time with the agency.

The former Harvard medical professor and head of infectious diseases at Massachusetts General Hospital was also criticised during the pandemic, particularly for her agency's sometimes chaotic communications.

Biden praised Walensky in a statement, saying she had "saved lives with her steadfast and unwavering focus on the health of every American."

"(S)she led a complex organization on the front lines of a once-in-a-generation pandemic with honesty and integrity," he wrote, adding that he wished her the best.

There was no immediate announcement on who would replace her.