Food and Drug Administration Commissioner Stephen Hahn promised that "science will guide our decision" for a coronavirus vaccine at a Senate hearing on Wednesday.

Why it matters: More Americans are expressing doubt about a first-generation vaccine, despite President Trump's efforts to push an unrealistic timeline that conflicts with medical experts in his administration.

• Hahn's testimony follows a slew of recent reporting that suggests deep politicization of the Trump administration's response to the pandemic.
• The FDA has reportedly been working to toughen the requirements for an emergency use authorization for a vaccine, which would make it almost impossible for one to be ready by Election Day.

What he's saying: "Decisions to authorize and 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," Hahn said.

• "FDA will not permit any pressure from anyone to change that. I will fight for science, Mr. Chairman. I will fight for the integrity of the agency, and I will put the interests of the American people before anything else."
• "In the end, FDA will not authorize or approve a vaccine that we would not feel comfortable giving to our families."