Shares of Humana Inc. HUM, -20.15% tumbled 13.0% toward a three-month low in afternoon trading Thursday, to pace the S&P 500’s SPX, +0.14% decliners, after the health insurance services company slashed its full-year membership estimate for its Medicare Advantage products. Humana’s stock was headed for the biggest one-day selloff since it slid 13.9% on March 16, 2020. Humana disclosed earlier Thursday that it now expects 2022 net membership growth for its individual Medicare Advantage products of 150,000 to 200,000 members, down from a previous estimate of 325,000 to 375,000 due primarily to “higher than anticipated terminations” during the annual election period, combined with expectations of higher than originally expected terminations for the rest of 2022. The company expects 2022 adjusted earnings per share of approximately $20.50, compared with the FactSet consensus of $20.53. Meanwhile, for the Humana Premier Rx Plan (PDP), the company now estimates a net membership decline of 125,000 members in 2022, compared with previous estimates of a loss of “a few hundred thousand members,” citing better-than-expected sales of the Walmart Value plan and lower-than-anticipated terminations. Among other health insurers, shares of UnitedHealth Group Inc. UNH, -4.01% dropped 1.9% and Anthem Inc. ANTM, -3.98% slumped 1.6%.