Rochelle Walensky, the director of the Centers for Disease Control and Prevention, is stepping down June 30. She made the announcement during an all-staff meeting Friday, crying as she finished her remarks, according to employees who tuned in.

Walensky, who has come under fire for the CDC's failure to respond effectively to the coronavirus pandemic, had announced plans last year for extensive changes, including faster release of scientific findings and easier-to-understand guidance.

Within minutes of Walensky's announcement, the White House sent out a statement from President Joe Biden praising her "steadfast and unwavering focus on the health of every American."

"As Director of the CDC, she led a complex organization on the front lines of a once-in-a-generation pandemic with honesty and integrity," Biden said. "She marshaled our finest scientists and public health experts to turn the tide on the urgent crises we've faced. Dr. Walensky leaves CDC a stronger institution, better positioned to confront health threats and protect Americans. We have all benefited from her service and dedication to public health, and I wish her the best in her next chapter."

Walensky also reflected on her tenure in an email to staff on Friday.

"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. I took on this role with the goal of leaving behind the dark days of the pandemic and moving CDC - and public health - forward into a much better and more trusted place," Walensky wrote, touting the administration of hundreds of millions of vaccines. "In the process, we safely opened schools and businesses, saved and improved lives, and protected the country and the world from the greatest infectious-disease threat we have seen in over 100 years."

Walensky's tenure was marked by tensions with Republicans, who have launched probes into whether the CDC coordinated its school-opening guidance with teachers' unions. Both Republicans and Democrats have criticized the agency's mixed messaging on when to wear masks, isolate when infected and take other precautions.

Jeff Zients, White House chief of staff, had developed frustrations with Walensky and her communication style during his tenure as COVID coordinator in 2021 and in early 2022, according to current and former White House officials. They said Walensky went off-script during a March 2021 COVID briefing when she spoke of a feeling of "impending doom" about a potential COVID surge.

Zients met earlier this year with Walensky to discuss her future in the administration, said two people who spoke on the condition of anonymity to discuss internal White House conversations.

Walensky's departure will create another hole in the most senior ranks of the nation's health leadership, with White House COVID coordinator Ashish Jha set to leave this month, former infectious-disease director Anthony S. Fauci recently retired and no confirmed head of the National Institutes of Health. The White House also has yet to name a director for its new pandemic response office, which is set to inherit some pandemic-preparedness work after the White House COVId response team disbands this month. Sen. Bernie Sanders, I-Vt., chairman of the Senate health panel, this week vowed that future nominees to lead CDC and other health agencies must commit to an agenda of drug-price cuts.