Big money is pouring into primary care clinics as the nation's health care giants hunt for ways to cut costs by keeping people healthy.

CVS Health said Wednesday that it will spend about $10.6 billion to buy Oak Street Health, which runs clinics that specialize in treating Medicare Advantage patients.

The acquisition comes just three months after a nearly $9-billion investment by rival Walgreens in VillageMD's acquisition of the urgent and primary care chain Summit Health-CityMD. And that deal was announced two months after CVS said it would spend $8 billion to acquire home health care provide...