Earlier this week, the Food and Drug Administration overruled—to much criticism—its own scientific advisory committee and approved the Alzheimer’s treatment Aduhelm. The agency made this decision despite thin evidence of the drug’s clinical efficacy and despite its serious side effects, including brain swelling and bleeding. As a result, a serious risk now exists that millions of people will be prescribed a drug that does more harm than good.

Less appreciated is how the drug’s approval could trigger hundreds of billions of dollars of new government spending, all without a vote in Congress or indeed any public debate over the drug’s value. Aduhelm’s manufacturer, Biogen, announced on Monday that it would price the drug at an average of $56,000 a year per patient, a figure that doesn’t include the additional imaging and scans needed to diagnose patients or to monitor them for serious side effects.

The federal government will bear the brunt of the new spending. The overwhelming majority of people with Alzheimer’s disease are eligible for Medicare, the federally run insurance program for elderly and disabled Americans. If even one-third of the estimated 6 million people with Alzheimer’s in the United States receives the new treatment, health-care spending could swell by $112 billion annually.