The Biden government has vetted other candidates besides Dr. Woodcock, but nobody has been publicly announced as the nominee from the sixth month of the president’s term. A spokesman for the White House wouldn’t comment on the delay, or about the candidates in contention. But some men and women who are still thought to be in the running include: Dr. Joshua Sharfstein, a former high-ranking F.D.A. official and a vice dean for public health at Johns Hopkins University and Dr. Florence Houn, a former F.D.A. official and past vice president at Celgene who now work as a consultant.

One recent addition to the roster is Dr. Michelle McMurry-Heath, a medical doctor and molecular immunologist who served as an associate science director of the F.D.A. throughout the Obama administration. But Dr. McMurry-Heath’s candidacy would be complicated by her current job as head of the Biotechnology Industry Association, which lobbies on behalf of biotech businesses.

In interviews, current and former F.D.A. employees and industry executives cited several pressing priorities as the country emerges from the coronavirus pandemic that gripped the nation.

The agency will soon decide whether to grant permanent approval to the three Covid vaccines currently in wide distribution under emergency use authorizations, Pfizer-BioNTech, Moderna and Johnson & Johnson. AstraZeneca and Novavax are hoping to submit applications for emergency use authorizations for their vaccines soon. They are finishing collecting data from their U.S. Phase 3 trials. AstraZeneca is already approved in other countries, even though some have restricted its use due to side effects. Novavax is not yet approved elsewhere. Sanofi is also in Stage 3 of clinical trials and expects to apply in the autumn.

The federal government poured more than $19 billion into vaccines, but less than half of that into therapeutics. The Biden administration has called for a renewed focus on development of treatments for Covid and its complications. Several therapies — remdesivir, monoclonal antibodies and the steroid dexamethasone — have improved the results for some Covid patients, but they do not work for everyone.

The F.D.A. has promised a new system, known as BEST, for monitoring adverse reactions to the Covid vaccines, but it is still not up and running as promised. Meanwhile, the F.D.A. and the Centers for Disease Control and Prevention are relying heavily on elderly tracking systems which they admit are deeply flawed, chiefly because they rely on patients or health providers to report what they believe to be bad reactions to the vaccine without providing evidence. The bureau is under increasing pressure to fix the system.

For years, clinics, academic institutions and industrial labs have pressed the F.D.A. to let them create their own in-house tests for various ailments without agency oversight. For just as long, the F.D.A. has resisted. But in August, the Trump administration ordered the agency to allow these lab-developed tests for use to detect numerous illnesses including Covid-19, without first verifying they work.