The F.D.A. is set to release a plan to issue stricter guidelines for the emergency authorization of any new coronavirus vaccine, which would add a new layer of caution to the vetting process, even as Mr. Trump has insisted a vaccine will be ready as early as next month. The guidelines may be formally released as early as this week if approved by the White House, and would recommend that clinical trial data be vetted by a committee of independent experts before the F.D.A. takes action, according to several people familiar with the draft.
On Wednesday, Dr. Hahn said that science would guide decisions by staff members about granting emergency approval to any Covid-19 vaccine, and that the F.D.A. “will not permit any pressure from anyone to change that.” The agency would not approve any vaccine that its officials would not give to their families, he said. His agency, he said, will seek the guidance from a panel of outside experts and the process “will be transparent and independent.”
Opening the hearing, Senator Lamar Alexander, chairman of the committee, urged Congress to start planning for the next pandemic, warning that experts say one could come as soon as next year. “We must act now to stop the cycle of panic, neglect, panic,” he said.
Senator Patty Murray, the top Democrat on the Senate Health Committee, told Dr. Hahn and Dr. Redfield that she intends to question them about Mr. Trump’s attempts to undermine them and “sabotage the work of our scientists and public health experts for his own political advantage.”
Dr. Fauci told the committee that federal scientists are beginning to study so-called “long-haulers” — people who suffer long-term side effects of coronavirus infection, including fatigue, fever, neurological problems and cognitive abnormalities. In addition, scientists have found “a disturbing number of individuals” who appeared to have recovered have inflammation of the heart, he said.
The Senate hearing follows upheaval within the federal Department of Heath and Human Services, whose top spokesman, Michael R. Caputo, took medical leave last week after delivering an outlandish rant on Facebook Live in which he accused C.D.C. scientists of sedition, promoted conspiracy theories and warned of armed revolt.
Mr. Caputo’s Facebook appearance came after the revelation that he and his science adviser, Dr. Paul Alexander, had tried to pressure the agency to revise or delay its weekly scientific reports. Dr. Alexander has since left the department. Democrats will almost certainly use the hearing to question Dr. Redfield about those events.