University of Oxford, which is collaborating on a COVID-19 vaccine with AstraZeneca, is now enrolling children between the ages of 6 years and 17 years and 8 months in their U.K. vaccine trial. Moderna started testing its RNA-based gene therapy on American children between the ages of 12 and 17 in December 2020, and the first Pfizer trials involving adolescents began in mid-October 2020. In China, Sinovac and SinoPharm trials have been enrolling children as young as 3.