Rand Paul vows GOP 'not done' with Fauci on COVID origins: 'He's been lying from the beginning'

Republican leadership is pressing forward with investigations into the "judgment" of outgoing National Institute of Allergy and Infectious Diseases (NIAID) Director Dr. Anthony Fauci, specifically on his connection to the origins of the COVID-19 pandemic. 

Sen. Rand Paul, R-Ky., who has been an outspoken critic of Fauci, joined "America Reports" on Thursday to discuss his ongoing search for answers and accountability.

"We're not done with him yet," Paul said. "I think Dr. Fauci actually made one of the worst judgments in modern medical history by funding for over a decade of dangerous gain-of-function research, which many of us believe leaked from the lab, inadvertently."

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Gain-of-function research often includes intentionally altering viruses to be more pathogenic or transmissible as a means to develop preemptive treatments for deadly diseases. Senate Republicans argue this research, which Fauci denies the National Institutes of Health (NIH) funded on coronavirus in Wuhan, could be responsible for an outbreak at the lab, leading to the global pandemic.

In 2014, the Obama administration paused new funding of gain-of-function research to "assess the potential risks and benefits." However, it was reinstated by the NIH in 2017.

In a letter sent in November to the White House's Office of Science and Technology Policy, five Republican senators demanded a fresh pause on gain-of-function research, saying there is a need to further evaluate its risks following the pandemic.

"For the past decade, [Fauci's] been an advocate of gain-of-function research. This debate started around 2010. He came down as a firm advocate for publishing this dangerous research and continuing to fund it," Paul told co-anchor Sandra Smith. 

"And this was a really, really bad mistake in judgment, and it may well have led to the deaths of 6 million people."

According to government documents obtained by The Intercept, the NIH during Fauci's tenure at the NIAID funded gain-of-function research at the Wuhan Institute of Virology.

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"It does connect Dr. Fauci to the origins of the pandemic. His support for this type of research without sufficient controls, without sufficient background and vetting of the projects, may well have led to one of the greatest man-made catastrophes in modern history," Paul said.

"He should apologize to the American people, but he should start telling the truth. He's been lying from the beginning."

Fox News' Sarah Rumpf and Patrick Hauf contributed to this report.