As the U.S. rushes to vaccinate its population against the coronavirus, most counties with the sickest residents are lagging behind and making only incremental progress reaching their most vulnerable populations. A ProPublica analysis of county data maintained by the CDCshows that early attempts to prioritize people with chronic illnesses like heart disease, diabetes and obesity have faltered. At the same time, healthier — and often wealthier — counties moved faster in vaccinating residents, especially those 65 and older.