Given that health care workers are tested frequently, are largely vaccinated, and must be masked, “the chances of causing a significant amount of infections seem very low” if isolation periods are shortened, said Dr. Bob Wachter, chairman of the department of medicine at the University of California, San Francisco.

“The consequences of keeping them out of the work force are massive when you think about the impact on health,” he added. U.C.S.F. also is weighing whether to reduce the isolation period to five days for workers: “I don’t know if five days saves us, but it’s better than seven and better than 10.”

Dr. Jha stressed, though, that more research is needed to definitively answer questions regarding how long a person with an Omicron infection may remain infectious. The variant is far more contagious than previous versions of the coronavirus.

The pandemic has exacerbated labor shortages that plague both hospitals and nursing homes: Nurses, aides and other workers have suffered extensive burnout and many have left the field for more lucrative work. Just this week, President Biden said that 1,000 military medical professionals would be deployed to help hospitals, and the National Guard is already working in some nursing homes and hospitals to address understaffing in several states.

Getting medical staff back to work sooner is the aim of several policy changes at hospitals that are reporting higher caseloads. Along with a shorter time frame for isolation, the policies include requirements regarding testing, vaccination status and symptoms.

Hospitals welcomed the revised guidelines. “Today’s announcement from the C.D.C. will allow health care workers to safely return to caring for patients sooner, which will help to alleviate the severe work force shortage crisis facing hospitals across the country,” said Nancy Foster, vice president of quality and patient safety policy for the American Hospital Association.

In New York State, which has reported a seven-day average of more than 4,600 hospitalizations as Omicron cases soar, major hospitals recently changed isolation protocols for vaccinated employees.