ST. LOUIS — Drops in coronavirus transmission rates in the St. Louis area are beginning to stall, raising concerns that residents are dropping their guard too soon and that caseloads could soon rise again. The St. Louis Post-Dispatch reports that the number of daily new coronavirus infections fell precipitously after a peak in January. Missouri’s seven-day average dropped below 500 a day last month, for the first time since last summer. At the same time, the St. Louis region’s daily average hospital admissions tumbled to 35, the lowest in eight months. Meanwhile, the region is now on track to reach widespread immunity by late June — with about 75% of the adult population vaccinated — an expectation weeks better than mid-August estimates made just last month.