By Manas Mishra and Michael Erman (Reuters) -The U.S. Food and Drug Administration on Friday authorized two COVID-19 vaccines for children under 5, opening the door to vaccinating millions of the country’s youngest children once the Centers for Disease Control and Prevention agrees. The FDA authorized Pfizer-BioNTech’s COVID-19 vaccine for children aged 6 months to 4 years and Moderna Inc’s shot for those 6 months to 17 years. Pfizer’s is already authorized for those over the age of 5. The vaccines could be rolled out to the under-5 age groups as early as next week, White House officials have …