Centene Corp. withdrew its 2025 earnings guidance late on 1 July after an early look at Affordable Care Act marketplace data showed far sicker members than the company had priced for. The health insurer said the revised morbidity assumptions would cut next year’s net risk-adjustment revenue by roughly $1.8 billion, or about $2.75 a share in earnings, and warned of higher Medicaid medical costs in key states. The surprise disclosure triggered a broad sell-off in managed-care stocks. Centene’s shares collapsed as much as 40% on 2 July, closing at an eight-year low of $33.78 and wiping out about $11 billion of market value in their steepest one-day decline since 2006. UnitedHealth, Humana, Cigna, Molina Healthcare and Elevance Health also retreated amid concerns that the ACA risk pool has deteriorated in 2025. Reporting results on 25 July, Centene posted an adjusted second-quarter loss of $0.16 per share on revenue of $48.74 billion, missing profit expectations even as sales topped forecasts. Its medical cost ratio jumped to 93% from 87.6% a year earlier. Management reinstated 2025 guidance at about $1.75 of adjusted earnings per share—roughly three-quarters below Wall Street’s prior consensus and far beneath the company’s earlier goal of more than $7.25—after lifting the projected revenue hit from ACA risk adjustment to $2.4 billion. Chief Executive Officer Sarah London told investors the insurer is repricing all marketplace plans and expects margin improvement across Medicaid, Medicare Advantage and marketplace products by 2026. The stock, which initially dropped a further 16% in pre-market trading after the earnings miss, ended the session up about 5% as investors weighed the revised outlook against steps to restore profitability.