President Biden announced his choice for secretary of health and human services on Dec. 7. He named the director of the Centers for Disease Control and Prevention the same day. But he has said nothing about who will lead another critical health agency on the front lines of battling the coronavirus pandemic: the Food and Drug Administration.

The silence is causing some consternation among FDA veterans, as well as public health and pharmaceutical experts, who say the agency needs a permanent head as it grapples with life-or-death decisions about coronavirus vaccines and treatments, while doing its day job of regulating products that account for 20 cents of every consumer dollar. That job includes approving cancer drugs, warning consumers about contaminated ice cream, and overseeing treatments for rare diseases in animals and humans.

A permanent leader also would help rebuild the credibility and morale of an agency whose reputation was hurt by the Trump administration’s relentless pressure and bashing, health-care experts say.

“The sooner there is a nominee who gets through the process, the better for public health and the handling of the pandemic,” said Stephen Ostroff, who twice served as acting FDA commissioner. “There are decisions that are more challenging when you are in an acting role,” especially at the beginning of an administration.

The lack of a nominee has helped fuel an increasingly bitter battle between supporters of the two people most frequently mentioned for the post: longtime FDA drug regulator Janet Woodcock and Johns Hopkins health expert Josh Sharfstein, a former top FDA official and former top Maryland health official. Biden named Woodcock acting commissioner after Stephen Hahn, the Trump administration’s last commissioner, left in January.

On Thursday, the contest heated up when 95 cancer experts, including a doctor who treated the late Beau Biden, the president’s son, told President Biden in a letter that Woodcock was “uniquely qualified” to be commissioner and praised her for overseeing the approval of dozens of major breakthroughs in treatments for cancer and other diseases.

The letter came just weeks after anti-opioid advocates voiced opposition to Woodcock, saying she and the drug center she helmed had approved too many opioids over the past two decades. Separately, several well-known public health experts have endorsed Sharfstein, saying he would bring fresh leadership to the agency.

The stakes are high: The next commissioner, besides grappling with a deadly and evolving pandemic, will determine the direction of an agency that has struggled to find the right balance between maintaining stiff requirements for drugs and devices and pressing for the quickest and most efficient approvals of medical products.

In broad terms, Woodcock, 72, is known for her deep experience in drug regulation and safety, and for prizing innovation, including in clinical trials, and regulatory flexibility. Sharfstein, 51, vice dean for public health practice and community engagement at Johns Hopkins Bloomberg School of Public Health, has wide experience in tobacco, food and opioid issues and was a proponent of greater transparency while at the FDA during the first Obama term.

Woodcock is often described as the more industry-friendly of the two, and someone with strong support among patient groups because of her determination to try new treatments for devastating and rare diseases. Sharfstein is favored by those who think the FDA should raise its drug-approval standards but is opposed by some patient advocates, including in the cancer community. That’s because he has talked about changing programs for expedited drug approvals — programs that some advocates say have benefited patients.

In an editorial Sharfstein wrote last year for the Journal of the American Medical Association, he said the FDA’s programs for expediting drug approval have created “a thicket of special programs, flexible review criteria, and generous incentives.” He called for changes to ensure that expedited drugs provide greater benefits to patients.

FDA observers say broad caricatures of Woodcock and Sharfstein don’t fully capture the experience and breadth of interests of two people who have spent decades working on some of the nation’s knottiest health issues.

“Both have dedicated their lives and careers to public health and public service,” said Jason Schwartz, an assistant professor of health policy at the Yale School of Public Health.

The situation was starkly different four years ago, he said, when President Donald Trump flirted with the idea of nominating a staunch libertarian as commissioner who believed the FDA should not review medical products for effectiveness — a cornerstone of the agency’s mission. “That would have blown up the FDA,” he added.

Woodcock and Sharfstein declined to comment for this article.

Past administrations have typically focused on the FDA job after deciding other higher-priority positions. Scott Gottlieb, the Trump administration’s first FDA commissioner, was nominated in March 2017 and sworn in that May. And unlike the CDC director, the head of the FDA must be confirmed by the Senate.

But the pandemic increases the urgency of installing a permanent commissioner, health experts say. Senior agency officials have expressed relief at the ascension of Woodcock, who is viewed as a stabilizing force; some prefer her to Sharfstein, who sometimes rubbed people at the agency the wrong way. “I can’t think of anybody” who would be better to run the agency right now, said Ostroff, the former acting commissioner. “She has vast experience, and she is not shy.”

Perhaps because of that, the Biden administration, which has a pressing to-do list, does not appear to be in a rush to nominate a permanent chief. Several people familiar with its thinking suggest that a nomination could come next month, after it deals with coronavirus relief legislation and the hoped-for confirmation of California Attorney General Xavier Becerra to be secretary of the Department of Health and Human Services. Becerra has emerged as a target for Senate Republicans. The White House did not respond to a request for comment.

The pro-Woodcock letter sent to Biden on Thursday was signed by 95 cancer researchers and center directors, many of whom helped guide the “cancer moonshot” Biden created in the last year of the Obama administration. Signers included Nobel laureates James Allison of the MD Anderson Cancer Center and Phillip Sharp of the Massachusetts Institute of Technology; immunotherapy pioneer Carl June of the University of Pennsylvania and pancreatic cancer specialist Elizabeth Jaffee of Johns Hopkins. W.K. Alfred Yung, a neuro-oncologist at the MD Anderson Cancer Center who cared for Beau Biden after his brain cancer was diagnosed, also signed the letter.

The endorsement by cancer experts came after anti-opioid advocates expressed vehement opposition to Woodcock, who served for years as head of the agency’s drug center. The groups argued that Woodcock and her division were too permissive in approving opioid medications and did not rein in drugmakers that falsely claimed that narcotic painkillers were less addictive. Democratic Sens. Maggie Hassan (N.H.) and Edward J. Markey (Mass.) also have sharply criticized Woodcock on opioids.

Woodcock supporters say that the epidemic represented a catastrophic failure by many segments of society and that it is not fair to blame her. Former FDA commissioner Robert Califf, who was Woodcock’s boss during his tenure at the end of the Obama administration, said the FDA was “far from perfect.” But he said doctors who vastly overprescribed the painkillers and pharmaceutical companies that pushed the pills were in large part responsible.

Some Woodcock critics also say she has presided over the lowering of FDA standards — a point her supporters strenuously reject. Those critics point to her approval of a drug for Duchenne muscular dystrophy, a rare genetic disease, over the vociferous opposition of a key agency reviewer and outside advisers. Although the approval was enormously popular among the parents of patients, it caused an uproar within the agency. Woodcock’s backers say she deserves credit for providing access to a drug for a devastating, terminal illness.

Sharfstein supporters point to his broad experience in public health and say that he would give more weight to issues such as tobacco and vaping and food safety. Besides being at the FDA, he also was Maryland’s health secretary and Baltimore’s health commissioner. He won praise for his overall performance but was criticized when the state’s health insurance exchange had severe problems during the rollout of the Affordable Care Act in 2013.