Policy & oversight
First Study of Medicare's Prior Authorization Pilot Finds Targeted Service Use Fell 15 to 20 Percent
A JAMA study of the WISeR model's first six months in six states found that certain Medicare services declined sharply, but researchers say the data cannot yet show whether the care not received was medically necessary or wasteful.
By the Goodsurance editorial teamOctober 28, 2026
When the Centers for Medicare and Medicaid Innovation launched the Wasteful and Inappropriate Service Reduction model, known as WISeR, in January 2026, it marked the first time traditional Medicare required prior authorization for certain services in any state. The pilot operates in Arizona, New Jersey, Ohio, Oklahoma, Texas, and Washington, covering services considered vulnerable to overuse and fraud, including epidural steroid injections for back pain, certain orthopedic procedures, and implanted nerve stimulators.
A study published in JAMA on October 26, 2026 provides the first empirical look at how the model changed care patterns. Researchers Hannah Neprash of the University of Minnesota School of Public Health and Michael Barnett of the Brown University School of Public Health used Epic Cosmos, an electronic health record dataset with more than 300 million patient records, to compare monthly service use in the six pilot states against all other states. The analysis covered the two years before the model launched and its first six months of operation.
Medicare's prior authorization pilot cut certain service use by up to 20 percent in 6 states. A new JAMA study can't yet say whether the care avoided was needed.
The study found that epidural steroid injections, the highest-volume WISeR-targeted service, declined about 15 percent compared with trends in non-pilot states. Other WISeR-targeted services declined roughly 20 percent. Services originally proposed for the model but never implemented showed no meaningful change, indicating that the prior authorization requirement itself drove the decline.
The researchers found the effect was strongest immediately after launch. For epidural injections, the measured reduction fell from about 21 percent in the first quarter of 2026 to about 9 percent in the second quarter. For other targeted services, it declined from 21 percent to 18 percent over the same period. Lead author Neprash noted that the study cannot yet determine whether the care not received was unnecessary or medically needed. The WISeR model is scheduled to run through 2031.
In plain words
Medicare started a test program in January 2026 called WISeR. The program requires doctors to get special approval before giving certain treatments. It only runs in six states: Arizona, New Jersey, Ohio, Oklahoma, Texas, and Washington.
A new study looked at what changed in those six states. Researchers found that fewer patients got certain treatments after the program started. Back pain injections went down by about 15 percent. Other treatments in the program went down by about 20 percent. Treatments not in the program did not change. That means the approval rules caused the drop.
The effect was biggest right after the program began. Over the next few months, the drop got smaller. Researchers say they still do not know if the treatments that were not given were needed or not needed. The program is planned to keep going until 2031.
Understand the basics first
Source: University of Minnesota School of Public Health
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