About 20 million adults have gained health coverage under the Affordable Care Act, according to a new report by the Department of Health and Human Services. The estimate includes 17.7 million adults under age 65 who gained coverage since October 2013, when the ACA’s Health Insurance Marketplaces opened, and 2.3 million adults who gained coverage under a provision allowing young adults to stay on a parent’s health plan until age 26. The uninsured rate for adults under 65 fell from 20.3% in October 2013 to 11.5% last month, according to agency’s analysis of data from the Gallup-Healthways Well-Being Index. Uninsured rates fell by more than 50% for black and white adults, and 27% for Hispanic adults.