Dr. Rochelle Walensky, who took over leadership of the Centers for Disease Control and Prevention on President Joe Biden's first day in office, has submitted her letter of resignation.

Walensky did not specify a reason for her departure, CNBC reported, but her resignation came on the day the World Health Organization announced an end to the COVID-19 global public health emergency. The U.S. had already announced its national public health emergency will expire next Thursday.

Walensky took over CDC leadership in January 2021, as COVID vaccines were just becoming available.

"She helmed the public health agency while the national pandemic response faced repeated setbacks from the emergence of the delta and omicron variants," CNBC reported.

“I have never been prouder of anything I have done in my professional career,” Walensky said, according to The New York Times.

In an email to CDC staff, Walensky said the agency had overseen the administration of more than 670 million vaccine doses and “protected the country and the world from the greatest infectious disease threat we have seen in over 100 years.”

Her last day will be June 30.

The Times reported that Walensky "broke down in tears" and expressed "mixed emotions" about leaving during an agency-wide conference call.

An expert on HIV, Walensky led the infectious disease division at Massachusetts General Hospital and was a Harvard Medical School professor before coming to the CDC, according to CNBC.

President Joe Biden's statement on Walensky's departure was glowing.

"Dr. Walensky has saved lives with her steadfast and unwavering focus on the health of every American," Biden's statement read.

"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.  We have all benefited from her service and dedication to public health, and I wish her the best in her next chapter."

Not everyone spoke so highly of the departing medical chief.

Rep. Ronny Jackson of Texas was among those taking parting shots at Walensky, tweeting, "Rochelle Walensky was responsible for spreading some of the WORST misinformation about COVID & the vaccine. She allowed the RADICAL teachers unions to write official CDC guidelines on school closures. GOOD RIDDANCE to Rochelle!!"

Rochelle Walensky was responsible for spreading some of the WORST misinformation about COVID & the vaccine. She allowed the RADICAL teachers unions to write official CDC guidelines on school closures. GOOD RIDDANCE to Rochelle!!

— Ronny Jackson (@RonnyJacksonTX) May 5, 2023

Others linked Walensky to a vaccine they said caused a rise in health problems.

🚨 BREAKING: Rochelle Walensky, is resigning as @CDCDirector. The rats are leaving the sinking ship. But even Walensky will have to face responsibility. No amnesty! pic.twitter.com/2LwGvcJGky

— Dr. Simon Goddek (@goddeketal) May 5, 2023

Dailyclout and @akamerica broke story: Pfizer finds dead, injured babies April 20 2021; Dr Walensky’s WH press conference tells pregnant women to take ‘safe’ mrna vaccination, April 23 2021. Dr Walensky resigned. You’re welcome. https://t.co/g6EaZiEnOt https://t.co/fWZ4clR4li

— Dr Naomi Wolf (@naomirwolf) May 5, 2023

It is unclear who will lead the CDC after Walensky's exit.

This article appeared originally on The Western Journal.