Updated at 1:37 p.m. ET
Amid criticism from Democrats that politics may be guiding decisions at the nation's top health agencies, the commissioner of the Food and Drug Administration told Congress on Wednesday that a coronavirus vaccine would not be approved until it met "vigorous expectations" for safety and effectiveness.
"Decisions to authorize or approve any such vaccine or therapeutic will be made by the dedicated career staff at FDA through our thorough review processes, and science will guide our decisions," FDA commissioner Stephen Hahn told senators.
Hahn continued: "FDA will not permit any pressure from anyone to change that. I will fight for science ... I will fight for the integrity of the agency, and I will put the interests of the American people before anything else."
Four of the top federal officials responsible for managing the coronavirus pandemic all testified before of the Senate Health, Education, Labor and Pensions Committee.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases; Dr. Robert Redfield, director of the Centers for Disease Control and Prevention; Adm. Brett Giroir, the assistant secretary of health who is in charge of coronavirus testing, and Hahn all were questioned.
The hearing follows confirmation that the U.S. death toll from the coronavirus pandemic has topped 200,000 people.
Redfield told Congress that the CDC is in the process of conducting a large study to determine how widely the coronavirus has spread across the country.
"The preliminary results in the first round show that a majority of our nation, more than 90% of the population, remains susceptible," Redfield said.
Senate Minority Leader Chuck Schumer, D-N.Y., and Sen. Patty Murray, D-Wash., the committee's ranking member, called on Hahn and Redfield to testify earlier this month, citing what they called "political interference" in the public health agencies.
"It is painfully clear that the Trump administration won't stop the political interference which is threatening our response to this pandemic and putting lives in jeopardy on its own, so it is up to Congress to act," Murray wrote in a statement on Tuesday, introducing legislation that would create a task force to investigate such incidences.
There have been a number of controversial guidance changes from the CDC and FDA over the last few weeks.
This week, the CDC posted and then removed guidance saying the coronavirus spreads through aerosol particles.
On Wednesday, Murray grilled Redfield about those changes. The CDC director sought to brush off the concerns, saying the agency sometimes modifies guidance based on new data and evolving science.
In response to a question from Sen. Tim Kaine, D-Va., about the aerosol guidance, Redfield said the document that appeared was a draft that had not been technically reviewed by career staff. It was taken down, he said, and replaced with the original document until the aerosol guidance could face scientific review and then be re-posted.
Hahn came under fire on the eve of the Republican National Convention for overstating the potential impact of an FDA authorization to treat the coronavirus with plasma. He later backtracked and apologized.
In his opening statement, Hahn anticipated that criticism, assuring senators and the public that science, not politics, guides his agency's decision-making. He raised the plasma authorization as an example of the FDA representing "science in action."
"Often we must make real-time decisions based on ever-evolving data concerning a previously unknown, highly contagious virus that we are still learning about, and sometimes it is necessary to reverse decisions as new data emerge," he said. "It is akin to how a doctor might approach a patient in an emergency situation, constantly updating a treatment plan when new data emerge."
Pursuit of a vaccine
There are also concerns about efforts to fast-track a vaccine for COVID-19 and the timeline for getting it to the general population.
On Friday, Trump insisted "every American" would have a vaccine by April. Redfield testified last week that it could be six to nine months after the FDA authorizes a vaccine before it is widely distributed. Potential vaccines are currently being tested.
On the campaign trail, Democratic nominee Joe Biden said last week, "I trust vaccines. I trust scientists. But I don't trust Donald Trump."
To that end, Hahn tried to temper concerns about the vaccine, laying out how the approval process will work. He told senators that vaccine sponsors will submit applications for approval or authorization. Career scientists will review safety and efficacy data and an independent advisory panel will weigh in. The data and the decision will be made public, he said.
"In the end, FDA will not authorize or approve a vaccine we would not feel comfortable giving to our families," Hahn said.
All the officials, including Fauci, said they would trust a vaccine if it was approved or authorized by the FDA after vetting by scientists.
Fauci also answered several basic questions about the vaccine.
He told Sen. Lamar Alexander, R-Tenn., who was presiding over his last HELP Committee meeting before retirement, that a vaccine will be available without cost to the public. Scientists do not know yet whether it will be effective for everyone and for how long immunity will last, and that two of the vaccines in development will require two doses — and another will require just one, Fauci said.
The officials also reiterated that even once a vaccine or vaccines are approved, it will be several months before they are practically available to everyone — and that because a vaccine will likely not be 100 percent effective, it will remain crucial for Americans to continue wearing masks, social distancing and taking part in testing and contact-tracing.
Redfield made that point at a hearing earlier this month and reportedly faced backlash from President Trump.
Asked on Wednesday by Sen. Tina Smith, D-Minn., whether Redfield had faced any political retribution, he responded: "I'm just going to stay with my comment that I'm going to present science and data as I see it."