Endeavor Health, the Chicago-area hospital system formed from the merger of NorthShore and Edward-Elmhurst, says it will step outside Aetna’s Medicare Advantage network starting Jan. 1, 2027. The change reaches patients who use an Aetna Medicare Advantage plan at Endeavor’s hospitals and clinics, though two groups keep their in-network access. Illinois state retirees enrolled in the Total Retiree Advantage Illinois, or TRAIL, MAPD PPO plan are exempt, and so are members of an Aetna PPO ESA plan.
The announcement lands squarely inside this year’s Medicare Annual Enrollment Period, the stretch each fall when people can switch Medicare Advantage or Part D plans for the coming year. Endeavor’s own notice ties its advice directly to that calendar rather than leaving patients to work out the timing on their own. Health systems drop out of insurance networks for reasons that rarely make it into a patient-facing notice, most often a dispute over the rates an insurer pays for care, and Endeavor’s page does not say why the Aetna relationship is ending.
What Endeavor Health says takes effect January 1
On its Medicare resources page, Endeavor Health states plainly: “Beginning Jan. 1, 2027, Endeavor Health will no longer be in-network for Aetna Medicare Advantage plans.” The health system runs hospitals and physician practices across Chicago’s northern and western suburbs, so the exit affects anyone who sees an Endeavor doctor or uses an Endeavor hospital while carrying an Aetna Medicare Advantage plan that falls outside the two exempted categories.
What a network exit doesn’t do: Endeavor leaving Aetna’s Medicare Advantage network says which relationship is ending, not which alternative plan keeps the same doctors and drug costs. The cost calculator spreadsheet and provider call script in The 2027 Medicare Open Enrollment Decision Kit support comparing plans on cost, drugs and doctors before a switch.
Who is exempt, and why the carve-out exists
The TRAIL MAPD PPO plan covers retired State of Illinois employees under a state-run retiree health program, and Endeavor’s page specifies that “State of Illinois retirees that participate in the Total Retiree Advantage Illinois (TRAIL) MAPD PPO plan” keep their in-network access after Jan. 1. Illinois’ Department of Central Management Services describes TRAIL as Medicare Advantage Prescription Drug coverage for retirees, annuitants and survivors of the state employee, teacher and college insurance programs, administered through its own Bureau of Benefits rather than by any single carrier. Aetna PPO ESA members, a separate employer-sponsored Aetna Medicare Advantage product, are exempt as well. Endeavor does not explain the carve-out beyond naming it, but the practical effect is that these two member groups can continue seeing Endeavor providers without disruption while other Aetna Medicare Advantage members cannot. TRAIL covers a large share of the state’s public retirees, so the exemption means the network change is narrower than a blanket Aetna exit would be, even though Endeavor’s page still describes it as a full departure from Aetna’s broader Medicare Advantage book of business.
Which Medicare Advantage plans remain in network
Endeavor’s page lists which coverage still works at its facilities after the Aetna exit: “Blue Cross Blue Shield of Illinois, Essence Healthcare, Humana, and UnitedHealthcare” remain in-network Medicare Advantage options, and the system continues to accept traditional Medicare. A patient who wants to keep an Endeavor doctor without qualifying for either Aetna exemption would need to weigh switching to one of those remaining plans, or to Original Medicare, during the current enrollment window. None of those four alternatives carries the same premium, drug formulary or provider referral rules as an Aetna plan, so a switch made only to preserve access to an Endeavor doctor can still change what a patient pays for other care entirely.
The Dec. 7 deadline Endeavor points to
Medicare’s Open Enrollment Period runs Oct. 15 through Dec. 7 each year, and it is the only broad window in which most Medicare Advantage members can change plans for Jan. 1 without a special circumstance. Endeavor’s page urges patients to review their insurance options “by December 7, 2026,” tying its network change to that same federal deadline rather than a date the health system set on its own. Missing the window generally means waiting for the Medicare Advantage Open Enrollment Period that follows, which runs Jan. 1 through March 31 and allows only one plan switch, so a patient who wants to keep continuity of care at an Endeavor facility has a narrower path to correct course after the new year begins.
The comparison a network exit leaves undone
Endeavor’s notice names the date and the two exempt groups, but it does not compare the remaining Aetna alternatives against Blue Cross Blue Shield of Illinois, Essence, Humana or UnitedHealthcare on cost, drug coverage or which doctors stay covered. That comparison falls to each enrollee, inside the same enrollment window Endeavor’s own page points to…