The Trump administration is standing by a rule that preserves payments to Obamacare health insurers that cover the sickest enrollees.

The rule provides certainty for a program under the Affordable Care Act’s that is designed to keep insurers in the individual health insurance markets, Centers for Medicare & Medicaid Services Administrator Seema Verma said in a Dec. 7 release.

The “risk adjustment” rule is integral to the Affordable Care Act’s goal of covering everyone, regardless of medical conditions. It requires...