Dec 5 (Reuters) - Pfizer Inc and its German partner BioNTech SE said on Monday they have submitted an application to the U.S. Food and Drug Administration (FDA) for emergency use authorization of their Omicron-adapted COVID-19 vaccine booster for children aged 6 months through 4 years. (Reporting by Leroy Leo in Bengaluru; Editing by Krishna Chandra Eluri)