Rochelle Walensky is leaving her role as head of the Centers for Disease Control and Prevention (CDC), the White House announced Friday.

Walensky’s exit comes days before the federal government is set to end the declaration of a public health emergency around COVID-19. She has led the agency since the start of the Biden administration in January 2021.

“Dr. Walensky has saved lives with her steadfast and unwavering focus on the health of every American,” President Biden said in a statement. “As Director of the CDC, she led a complex organization on the frontlines of a once-in-a-generation pandemic with honesty and integrity. She marshalled 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,” Biden added. “We have all benefited from her service and dedication to public health, and I wish her the best in her next chapter.”

Walensky previously served as chief of the Division of Infectious Diseases at Massachusetts General Hospital. She took over as head of the CDC at a time when the agency was seeking to restore credibility after it was largely sidelined and, at times, politicized during the Trump administration’s initial response to the coronavirus pandemic.

Biden took office before COVID-19 vaccines were widely available to the public, and she led messaging efforts on vaccination efforts and evolving recommendations on testing, masking and how many doses of the shot would be required.

But as more Americans were vaccinated and restrictions around the pandemic eased, Walensky and the agency came under scrutiny for how it conveyed new information to the public.

In May 2021, the CDC changed its guidelines to state that fully vaccinated individuals did not have to wear a mask indoors, a move that was criticized by some health experts for muddling the messaging around the state of the pandemic and changing the guidance too quickly when many Americans were still not vaccinated.

In late 2021, the CDC announced that infected Americans would need to isolate for only five days, not 10, if they were no longer experiencing symptoms or if their symptoms were improving, and that a negative test result would not be required to end the isolation period.

Confusion and criticism ensued, as public experts said the agency erred by not specifying the need for a negative test before leaving isolation.

The CDC in January announced a reorganization of the agency after Walensky said it did not “reliably meet expectations” during the COVID-19 pandemic. The overhaul included the creation of several new offices and a shift in reporting structure among officials at the CDC.

Walensky’s departure comes at a time when concerns around COVID-19 have largely faded into the background for many Americans.

Biden last September said the pandemic was “over” in a nod to it no longer influencing the day-to-day behavior of many Americas, while the administration’s formal public health emergency is set to expire next week.

Earlier Friday, the World Health Organization (WHO) announced it was downgrading its declaration of COVID-19 as a public health emergency of international concern (PHEIC), more than three years after it was first declared.

The coronavirus has killed roughly 1.1 million Americans since the outbreak began in early 2020.