“We see a unique methodological opportunity to evaluate the harms of low-value care,” wrote Allison H. Oakes, a health services researcher at the University of Pennsylvania, and Dr. Jodi B. Segal, a professor of medicine at Johns Hopkins.

As the pandemic took hold, elective surgeries were canceled and radiology equipment stood abandoned as patients and doctors avoided CT scans, M.R.I.s, mammograms and colonoscopies. Even prescriptions for antibiotics plummeted.

“We are in the midst of an unprecedented natural experiment that gives us an opportunity to determine the effect of a substantial decline in medical care utilization,” said Dr. H. Gilbert Welch, a senior investigator at the Center for Surgery and Public Health at Brigham and Women’s Hospital in Boston.