It’s not often that the American Hospital Association—known for fun lobbying tricks like hiring consultants to create studies showing the benefits of hospital mergers—directly goes after another consolidation in the industry.

But when the AHA caught wind of UnitedHealth Group subsidiary Optum’s plans, announced in January 2021, to acquire data analytics firm Change Healthcare, they offered up some fiery language in a letter to the Justice Department. “The acquisition … will concentrate an immense volume of competitively sensitive data in the hands of the most powerful health insurance company in the United States, with substantial clinical provider and health insurance assets, and ultimately removes a neutral intermediary.”

If permitted to go through, Optum’s acquisition of Change would fundamentally alter both the health data landscape and the balance of power in American health care. UnitedHealth, the largest health care corporation in the U.S., would have access to all of its competitors’ business secrets. It would be able to self-preference its own doctors. It would be able to discriminate, racially and geographically, against different groups seeking insurance. None of this will improve public health; all of it will improve the profits of Optum and its corporate parent.

Despite the high stakes, Optum has been successful in keeping this acquisition out of the public eye. Part of this PR success is because few health care players want to openly oppose an entity as large and powerful as UnitedHealth. But perhaps an even larger part is that few fully understand what this acquisition will mean for doctors, patients, and the health care system at large.