By Michael Erman and Julie Steenhuysen (Reuters) – Moderna Inc said on Thursday it asked U.S. regulators to authorize its COVID-19 vaccine for children under the age of 6, which would make it the first shot against the coronavirus available for those under 5-years-old. The COVID-19 vaccine from Pfizer Inc and BioNTech SE is authorized for children 5 and older. But their trial results for 2- to 4-year-olds showed a weaker immune response than in adults, forcing the study to be extended to test a third dose. Pfizer has said that data would come in April. “This does represent an important area of…