Medicare Advantage in Alameda County, California
148,382 people in Alameda County, California were enrolled in Medicare Advantage in October 2026, 52.8% of 280,970 eligible beneficiaries (+0.5 pts since October 2025). Kaiser Foundation Health Plan, Inc. is the largest parent organization with 73% of reported enrollment; 23 parent organizations have 11 or more members and the HHI is 5,510 (highly concentrated). HRSA classifies the county as partly rural. For 2027, 6,916 members here are in plans that terminate or leave the county, and Elevance Health, Inc., Molina Healthcare, Inc., SANTA CLARA COUNTY HEALTH AUTHORITY and others leave. MA plans offered go from 22 to 16.
Parent organizations in Alameda County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| Kaiser Foundation Health Plan, Inc. | 108,683 | +4,110 | 73.4% |
| SCAN Group | 10,286 | +8,059 | 6.9% |
| UnitedHealth Group, Inc. | 8,365 | −1,144 | 5.6% |
| CVS Health Corporation | 7,729 | −2,427 | 5.2% |
| Alignment Healthcare USA, LLC | 5,174 | +1,107 | 3.5% |
| Elevance Health, Inc. | 2,555 | −582 | 1.7% |
| California Physicians' Service | 2,214 | −934 | 1.5% |
| Center For Elders Independence | 898 | +90 | 0.6% |
| Imperial Health Plan of California | 717 | +332 | 0.5% |
| Alameda Alliance for Health | 312 | new | 0.2% |
| On Lok, Inc. | 309 | +17 | 0.2% |
| Humana Inc. | 259 | +76 | 0.2% |
| Molina Healthcare, Inc. | 154 | −3,858 | 0.1% |
| Centene Corporation | 143 | −23 | under 0.1% |
| Chinese Hospital Association | 90 | −10 | 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, 37,104 beneficiaries in Alameda County were assigned to 181 Medicare Shared Savings Program ACOs, 47.8% of assignable Original Medicare beneficiaries. Together, roughly 75% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.