But vaccines appeared to be a major concern.
“Public confidence in vaccines is so important,” Dr. Hahn, the F.D.A. commissioner, said. “We have an obligation to use all of our scientific knowledge, regulatory framework to ensure that any vaccine that comes before us, whether for authorization or approval, meets our stringent standards for safety and effectiveness.”
Seven in 10 Americans have said they would get vaccines against the virus if immunizations were free and available to everyone, according to recent polling, a number that health officials fear may not be enough to achieve “herd immunity,” a term that signifies that a vast majority of a population has protection against infection. At least 70 percent will need to be immune to the virus to reach that point, according to researchers at Johns Hopkins University.
Dr. Redfield said that the plan was being developed with Operation Warp Speed, the Trump administration’s crash vaccine program that aims to have 300 million doses of a vaccine by early next year. Officials at the Defense Department and the Department of Health and Human Services involved in that project have spent significant time discussing a public-relations campaign that will, among other things, try to win over Americans suspicious of a coronavirus vaccine, according to a senior administration official.
The F.D.A. took steps to try to reassure people that the sped-up process would not come at the expense of safety, with Dr. Hahn announcing at the hearing that the F.D.A. would release guidelines to aid in the development and production of Covid-19 vaccines.
The F.D.A. will require that manufacturers prove their products are safe and effective through a clinical trial, and that the vaccine be at least 50 percent more effective than a placebo to win agency approval. The agency will also require manufacturers to track individuals who have been vaccinated for a year, to monitor them for any adverse reactions. There are currently more than 140 vaccines being developed against the coronavirus.
All four officials also appeared before House lawmakers last week, when Dr. Redfield warned of a potentially crippling second wave of the virus that would coincide with flu season.
In his opening remarks, Senator Lamar Alexander, the Republican chairman of the Senate health committee, called on Mr. Trump to occasionally wear a mask to eliminate what he called dangerous political divide between Republicans and Democrats over mask-wearing.