(AP) – New COVID-19 cases per day in the U.S. have doubled over the past three weeks, driven by the fast-spreading delta variant, lagging vaccination rates and Fourth of July gatherings. Infections jumped to an average of about 23,600 a day on Monday, up from 11,300 on June 23. And all but two states – Maine and South Dakota – reported that case numbers have risen over the past two weeks. Some parts of the country are running up against deep vaccine resistance.