Medicare Advantage in Contra Costa County, California
120,690 people in Contra Costa County, California were enrolled in Medicare Advantage in October 2026, 52.2% of 231,169 eligible beneficiaries (−1.0 pts since October 2025). Kaiser Foundation Health Plan, Inc. is the largest parent organization with 76% of reported enrollment; 17 parent organizations have 11 or more members and the HHI is 6,000 (highly concentrated). HRSA classifies the county as partly rural. For 2027, 3,978 members here are in plans that terminate or leave the county, and Molina Healthcare, Inc., SCAN Group, Elevance Health, Inc. and others leave. MA plans offered go from 6 to 5.
Parent organizations in Contra Costa County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| Kaiser Foundation Health Plan, Inc. | 92,139 | +4,337 | 76.5% |
| UnitedHealth Group, Inc. | 10,813 | +383 | 9.0% |
| Humana Inc. | 8,812 | +3,310 | 7.3% |
| Imperial Health Plan of California | 2,497 | +1,942 | 2.1% |
| California Physicians' Service | 2,297 | +122 | 1.9% |
| Elevance Health, Inc. | 1,275 | −982 | 1.1% |
| CVS Health Corporation | 977 | −16 | 0.8% |
| Contra Costa Health Services | 623 | new | 0.5% |
| Center For Elders Independence | 407 | +62 | 0.3% |
| Centene Corporation | 208 | −33 | 0.2% |
| Molina Healthcare, Inc. | 173 | −8,866 | 0.1% |
| SCAN Group | 96 | +69 | under 0.1% |
| Blue Cross Blue Shield of Michigan Mutual Ins. Co. | 43 | +1 | under 0.1% |
| Health Care Service Corporation | 17 | −9 | under 0.1% |
| Alignment Healthcare USA, LLC | 14 | new | under 0.1% |
CMS suppresses county and contract counts of 10 or fewer; shares are of reported enrollment.
Value-based care alongside MA
In PY 2024, 18,824 beneficiaries in Contra Costa County were assigned to 179 Medicare Shared Savings Program ACOs, 28.7% of assignable Original Medicare beneficiaries. Together, roughly 66% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.