As children head back to school, leaders in government, education and medicine are anticipating an uptick in COVID-19 spread. The expectations come as about 30 percent of children between the ages of 5 and 11 and 60 percent of 12- to 17-year-olds have completed a two-dose COVID vaccination series, according to the CDC — which also loosened pandemic guidance for schools following the tumultuous shutdowns of 2020.