The interview, which took place Tuesday on ABC News' Instagram Live, comes after the FDA commissioner was summoned to the White House to provide an update to President Donald Trump's chief of staff, Mark Meadows, on the status of the emergency use authorization for the vaccines.
Asked by Ashton to explain "what takes so long" to get the COVID-19 vaccines through the emergency use authorization process, Hahn explained the rigorous process the FDA goes through for approval.
He said a typical approval timeline for a set of vaccine clinical trials of this size -- Pfizer and BioNTech had 44,000 people in the trials and Moderna had 30,000 -- "would typically take between three and four months, maybe even longer to review all the data."
The FDA is now trying to get the process completed in about three weeks. Hahn said the FDA is looking at the manufacturing data, specifically the quality around manufacturing, the clinical data that shows whether the vaccine is safe and effective and the data surrounding adverse effects.
Hahn said the FDA and its scientists will ensure "vigorous standards are being enforced when we look at safety and efficacy" of these vaccines. "We need to be able to make this assurance to the American people," he said when asked about vaccine safety.
The vaccines that are being vetted by the FDA for emergency use authorization will require safety follow-ups even after they are approved. Hahn said should either of the vaccines get approved for emergency authorization, the FDA will mandate safety and efficacy follow-ups for a minimum of two years.
"As with any medical product ... there could be long-term side effects that we need to account for, which is why we put in place a very, very vigorous surveillance program," Hahn said.
The FDA is looking at the raw data from Pfizer and Moderna's clinical trials to ensure the safety and efficacy of the vaccines. "We just don't trust a press release. We're going to look at that data and we're going to do our own analysis. And then we're going to look by specific patient groups, we're going to look by ethnic groups, we're going to look at both safety and efficacy from a number of different ways."
Hahn said if the COVID-19 vaccines are as effective as the companies have reported -- with Pfizer and BioNTech reporting a 95% efficacy and Moderna reporting a 94.1% efficacy -- then "thousands if not hundreds of thousands of lives across the globe could be saved." The FDA will work to confirm those efficacy numbers in its review.
The FDA has been reviewing Pfizer's clinical trial data since receiving their emergency authorization approval application on Nov. 20. Moderna announced Monday it will ask the FDA for emergency use authorization for its COVID-19 vaccine. The FDA will hold public hearings about each of the vaccines on Dec. 10 and Dec. 17, respectively. Before the public hearings, the FDA will release documents summarizing their assessment of the vaccine applications. The FDA will make its official authorization decision after these hearings are held.
Pfizer and BioNTech expect to produce up to 50 million vaccine doses worldwide by the end of the year and up to 1.3 billion doses by the end of 2021. Moderna is on track to produce 20 million distributable doses by the end of the year, which is enough doses to vaccinate 10 million people in the U.S. The company is also on track to manufacture 500 million to 1 billion doses worldwide in 2021.
Ashton asked Hahn if people like pregnant women, children, people with kidney failure and other subsets of people who were not represented in the phase three clinical vaccine trials will be advised to take the vaccine.
"It's one of the things we'll have to look at," Hahn said. He said it's unlikely they will initially advise pregnant women to take the vaccine at first, "but we need to look at the data to do that."
"If we don't have data to support the use of a vaccine, we're going to come out and say that, and then we're going to have to make some decisions about that emergency use authorization process," Hahn told Ashton. "But that's the point of our looking at the data."
Asked if it's possible the FDA will come to one conclusion on the vaccines and the Centers for Disease Control and Prevention will come to another, Hahn said he and CDC Director Robert Redfield are "aligned." Once approved by the FDA, the CDC's Advisory Committee on Immunization Practices will meet to vote on whether to recommend the vaccine's use. The ACIP voted on Tuesday that health care workers and nursing home residents should be first to receive the vaccine.
"We're hand in glove with respect to sharing information. I expect that, in fact, we'll be very aligned moving forward, because the data has to drive the decision that we make with respect to allocation and prioritization," he said.
Hahn said the FDA is "cooperating fully" with President-elect Joe Biden's transition team and that recently they've undergone a pandemic preparedness and response effort to reflect on the lessons learned from their response to COVID-19. He said one of the main lessons the FDA learned was the need for more transparency.
"We need a lot more transparency about the information that goes into our emergency use authorizations. ... This is all about our being a learning organization, and improving moving forward," he said.
"We made a promise to the American people that we're not going to do shortcuts here," Hahn reiterated.