Keeping Health Insurance Affordable Act of 2017 This bill alters and establishes several programs relating to health insurance and prescription drugs. Among other changes, the bill establishes and funds the Individual Market Reinsurance Fund to provide an individual market stabilization reinsurance program in each state; requires the Department of Health and Human Services to establish a public health insurance option through health insurance exchanges; expands eligibility for the health insurance premium tax credit; expands eligibility for additional cost-sharing reductions that apply to certain enrollees of qualified health plans; requires drug manufacturers, as a condition of participation in the Medicare prescription drug benefit, to issue rebates to the Centers for Medicare & Medicaid Services (CMS) for drugs dispensed to certain low-income enrollees; requires the CMS to negotiate with pharmaceutical companies regarding prices for drugs covered under the Medicare prescription drug benefit; and provides an enhanced federal medical assistance percentage of 100% to states that deliver items and services through a collaborative care model or an evidence-based model that integrates behavioral health services into primary care treatment.