The FDA commissioner was summoned to the White House on Tuesday to conduct a briefing on the coronavirus vaccine approval process. President Trump’s chief of staff, Mark Meadows, called Dr. Stephen Hahn to brief officials at 9:30 a.m., on the same day that the Centers for Disease Control and Prevention (CDC) advisory panel is scheduled to meet regarding vaccine distribution plans.

The FDA is scheduled to meet on Dec. 10 regarding Pfizer’s application for emergency use authorization (EUA) of its coronavirus vaccine, three weeks after the company filed for it. The FDA plans to meet on Dec. 17 to discuss Moderna's EUA. Critics have questioned the delay in scheduling, including Fox News medical contributor Dr. Marty Makary, who said the agency is being “too bureaucratic.”

“The FDA has been too bureaucratic, taking too much time,” Makary said Monday, while appearing on “Bill Hemmer Reports.” “And I don’t know if they’re scheduling around vacation times and tee times of the reviewers, but they should turn the application around in 24 hours.”

DR. MARTY MAKARY BLASTS FDA TIMETABLE TO APPROVE CORONAVIRUS VACCINE

And on Monday, following Moderna’s announcement that it was ready to file for EUA, President Trump tweeted that the FDA must act quickly.

But on Tuesday, ahead of the briefing, Hahn said that the FDA’s scientists are taking the time they need to decide on approval.

DR. SCOTT ATLAS RESIGNS AS SPECIAL ADVISER TO TRUMP ON CORONAVIRUS

“Let me be clear – our scientists have to make the decision and they will take the time that’s needed to make the right call on this important decision,” Hahn said in a statement provided to Fox News. "We want to move quickly because this is a national emergency, but we will make sure that our scientists take the time they need to make an appropriate decision. It is our job to get this right and make the correct decision regarding vaccine safety and efficacy."

The agency’s scientists have been working non-stop on a “massive amount of data,” according to information provided to Fox News. The quickest approval process involving this amount of data ever completed before was 3.5 months, putting the current schedule on pace for historic speed.

CLICK HERE FOR COMPLETE CORONAVIRUS COVERAGE

An FDA spokesperson added that the thousands of pages of data must be divided up and reviewed by experts from different disciplines, and then integrated into an overall review. 

"Completion of these reviews involves such things as ensuring that the manufacturing process and the controls on manufacturing are appropriate, checking statistical analyses performed to ensure that they were done properly, and doing additional analyses, as necessary, to look at the effect of the vaccine on subsets of individuals who might be at greater risk of adverse effects," the spokesperson said. 

 As of Tuesday, the U.S. had tallied over 13.5 million cases of the novel coronavirus, and more than 268,103 deaths, which is nearly 100,000 more fatalities than the second-highest death toll in Brazil.

Fox News' John Roberts contributed to this report.