Medicare Advantage in Mason County, Illinois
1,474 people in Mason County, Illinois were enrolled in Medicare Advantage in October 2026, 41.5% of 3,551 eligible beneficiaries (+0.2 pts since October 2025). CVS Health Corporation is the largest parent organization with 53% of reported enrollment; 6 parent organizations have 11 or more members and the HHI is 3,534 (highly concentrated). HRSA classifies the county as fully rural. For 2027, 0 members here are in plans that terminate or leave the county. MA plans offered go from 25 to 18.
Parent organizations in Mason County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| CVS Health Corporation | 759 | +43 | 52.9% |
| Humana Inc. | 280 | +45 | 19.5% |
| UnitedHealth Group, Inc. | 251 | +20 | 17.5% |
| Centene Corporation | 100 | −7 | 7.0% |
| Molina Healthcare, Inc. | 34 | −8 | 2.4% |
| Health Care Service Corporation | 12 | +1 | 0.8% |
CMS suppresses county and contract counts of 10 or fewer; shares are of reported enrollment.
Value-based care alongside MA
In PY 2024, 1,074 beneficiaries in Mason County were assigned to 11 Medicare Shared Savings Program ACOs, 61.8% of assignable Original Medicare beneficiaries. Together, roughly 78% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.