U.S. Secretary of Health and Human Services Alex Azar praised the Centers for Disease Control and Prevention in a visit to the agency’s Atlanta headquarters on Wednesday, while also defending what some have called damaging interference in its work.

“The CDC is the premier epidemiological organization on the face of the planet," Azar said. But in a pandemic this unprecedented and widespread, he continued, other officials and agencies play a role as well.

Azar made the visit to promote the Trump administration’s “Warp Speed” development of a vaccine. He also toured Grady Memorial Hospital, which has treated hundreds of COVID-19 victims, and Emory University, where vaccine trials are underway. He spoke to reporters at the CDC, as did CDC Director Robert Redfield and CDC Deputy Director for Infectious Diseases Jay Butler.

The first doses of a vaccine could be available by the end of the year, Azar and Butler said.

“These are the questions that we are asking every day as we move forward with vaccine planning,” Butler said. “I wish I had a crystal ball. ... I think, looking at the current trends in the studies and the production of the vaccines, it’s reasonable to expect we will have at least one, possibly two products available before the end of the calendar year."

It will be offered first to priority groups until there’s enough for the entire population. Beyond the initial rollout, Butler did not suggest dates.

Azar did. He said he expected there would be enough by the end of the year to vaccinate the “most vulnerable," then enough by the end of January to vaccinate all seniors, health care workers and first responders. By the end of March or early April, Azar said, there should be enough to vaccinate all Americans who want one.

Like Butler, Azar said the rollout would be science-based.

“The system’s working,” Azar said. “This is being played by the book.”

Azar’s comment followed a week of searing criticism in local and national media. The trip not only serves to defend the administration’s adherence to science, but to shore up confidence in the process prior to offering a vaccine to the public.

Public refusal to take an eventual vaccine could spell disaster for the pandemic response. And polls have shown public confidence in a vaccine has fallen amid recent controversies. The president had suggested that a vaccine should be available before the election, and the White House reportedly fought the Food and Drug Administration’s effort to issue strong guidance for development of the vaccine.

The Atlanta Journal-Constitution and others have reported on an atmosphere of near-despair at the CDC, once the global gold standard for public health response. Azar, Redfield and others have often stood silent as President Trump and political aides have contradicted the agency’s scientists.

Last week, the dean of Emory University’s Rollins School of Public Health, Dr. James Curran, said the administration’s damage to the CDC’s work amid the pandemic has been “unforgivable.” And a lengthy article by the investigative news organization ProPublica cited political interference undermining the CDC in perhaps “the darkest chapter” in the agency’s history.

ProPublica obtained emails that Butler wrote early in the pandemic that were critical of administration’s censorship of CDC. The CDC was trying to caution people against singing in choirs because of the danger of sharing infected breath; the White House ordered that deleted. In Georgia, some of the earliest COVID-19 deaths were of attendees at a choir performance.

Wednesday, as Butler stood six feet to Azar’s right, Azar said the critics are likely speaking above their pay grade.

The pandemic is unprecedented and “impacts the entire government and the entire economy,” Azar said. "And I think some of the people who comment are — not having actually lived in or led this organization during this type of a crisis, fail to appreciate that,” Azar said.

“But make no mistake, the CDC is a science- and evidence-led organization. We respect CDC scientists conclusions," Azar said.

“That’s how we operate, that’s how we’re going to keep operating.”