WASHINGTON — The director of the Centers for Disease Control and Prevention on Tuesday defended the agency against accusations that federal scientists were being too slow to update their pandemic-control guidance and overly conservative with their recommendations, especially on outdoor mask wearing.
At a Senate hearing with other top federal health officials on the federal government’s pandemic response, Republicans accused the C.D.C.’s director, Dr. Rochelle P. Walensky, of accommodating special interests in the agency’s guidance for schools and of failing to recognize the low risk of outdoor transmission of the coronavirus.
They said that the agency had lost the trust of Americans looking to return to normal life.
Their complaints echoed mounting exasperation — even among some public health experts — with the federal government’s pace in relaxing its recommendations as states across the country move to reopen their economies.
Frustrations ranged from the practical — asking children to wear masks at camp — to the fantastic — suggestions that the National Institutes of Health had conspired with the Chinese to supercharge viruses, an accusation that Dr. Anthony S. Fauci called “entirely and completely incorrect.”
And they came as the White House moved to increase access to coronavirus vaccines with a new pledge from the ride-share giants Uber and Lyft, which President Biden said would begin offering free rides to and from tens of thousands of vaccination sites.
Senator Susan Collins, Republican of Maine, complained at the hearing that the C.D.C. had allowed the American Federation of Teachers to exert undue influence over its school reopening guidance, compromising its scientific integrity.
Dr. Walensky said that a change to the schools guidance was because of an “oversight” — its draft guidance had neglected to include materials on how to protect teachers with compromised immune systems. The back-and-forth was a normal part of the agency’s process for drafting guidance, she said, when agency scientists consider outside advice from industry experts. C.D.C. scientists wrote the recommendations themselves, Dr. Walensky said.
Ms. Collins also accused the C.D.C. of using faulty data in its recent mask guidance for the outdoors. The agency announced last month that “less than 10 percent” of transmission was occurring outdoors, a statistic infectious disease experts said was a misleading exaggeration. Dr. Walensky said that the C.D.C. had used a rigorous aggregation of studies in a renowned medical publication, The Journal of Infectious Diseases, to back that figure.
“We have unnecessary barriers to reopening schools, exaggerating the risks of outdoor transmission and unworkable restrictions on summer camps,” Ms. Collins said. “It matters because it undermines public confidence in your recommendations, in the recommendations that do make sense.”
Dr. Walensky said that the C.D.C. was working to update its guidance as more Americans get vaccinated and as scientists glean new insight. The agency’s drafting process — seeking internal and external expert input — was collaborative and responsive, she said.
Senator Bill Cassidy, Republican of Louisiana, told Dr. Walensky that the public was “beginning to disregard what you say that’s true,” warning of consequences if the C.D.C. did not update guidance on how Americans could return to the office. He also accused the agency of being slow to acknowledge the minimal risk of outdoor transmission.
“The American people have just lost patience with us,” he said.
As health officials defended the Biden administration’s work, the White House announced its latest moves to bolster the nation’s vaccinations. In a meeting with six governors from both parties, including Republicans from Ohio and Utah, Mr. Biden said that the ride-sharing initiative was part of an aggressive new phase of the administration’s efforts to address vaccine hesitancy and access.
The White House said that Uber and Lyft would promote the free rides until July 4, the target date of Mr. Biden’s goal of at least partly vaccinating 70 percent of adults.
Health officials have said that Americans remain eager to get inoculated — providers are administering about 2.19 million doses per day on average — but a lack of transportation has hindered access.
The Senate hearing on Tuesday was dominated by discussion of the C.D.C.’s guidance materials. Senator Richard M. Burr, Republican of North Carolina, linked the agency’s guidance-drafting process to the administration’s ability to get more Americans vaccinated.
“If we continue to fail at the trust that they have in us making the calls that are appropriate,” he said, then “we’re going to fail.”
Senator Lisa Murkowski, Republican of Alaska, said that her state was still waiting on the C.D.C. to update its cruise ship guidance, which was threatening to sap the state’s tourism industry.
She also said that federal mask requirements for transportation hubs were compromising the work of fishermen, who faced more danger in wearing a mask than not but who are fearful of failing to comply with the government’s orders.
“You’re out on a boat. The winds are howling. Your mask is soggy wet,” Ms. Murkowski said. “Tell me how anybody thinks that this is a sane and a sound policy.”
On the other side of the United States, fisherman were struggling with the same enforcement policies, said Senator Maggie Hassan, Democrat of New Hampshire. She said she had met with some in her state who had been fully vaccinated but nagged by members of the Coast Guard about keeping masks on.
Dr. Walensky said the agency was finalizing guidance to deal with the problem.
At one point on Tuesday, Senator Christopher S. Murphy, Democrat of Connecticut, stepped in to defend the officials testifying.
“We suffered through four years with a president who literally made things up about this virus, who simplified the story over and over and over again,” he said. “We still have a lot to learn. And so I, frankly, appreciate the fact that we have leaders today who recognize that we still have gaps in information who occasionally may err on the side of caution in order to save lives.”
The hearing took several heated detours to address accusations that the National Institutes of Health, where Dr. Fauci is a top official, had supported research in a laboratory in Wuhan, China, where some top Trump administration officials maintained the novel coronavirus might have leaked from. Most scientists agree that the coronavirus most likely emerged in the natural world and spread to humans from animals.
Senator Rand Paul, Republican of Kentucky, who is known for sparring with Dr. Fauci, accused the government’s top infectious disease expert of backing an American scientist’s collaboration with the Wuhan Institute of Virology. The institute houses a state-of-the-art laboratory known for its research on coronaviruses.
Dr. Fauci quickly shot down the suggestion about so-called gain of function research, saying the N.I.H. had never supported such work there.
Katie Rogers contributed reporting.