A healthcare worker prepares a Pfizer coronavirus disease (COVID-19) vaccination in Los Angeles, California, January 7, 2021.Lucy Nicholson | ReutersPfizer said it has started a clinical trial testing its Covid-19 vaccine on healthy 6-month to 11-year old children, a crucial step in obtaining federal regulatory clearance to start vaccinating young kids and controlling the pandemic.The first participants in the study have already gotten their shots, which were developed in partnership with German drugmaker BioNTech, New York-based Pfizer announced Thursday. It intends to enroll 144 children in the first phase.For the first phase of the trial, the company will identify the preferred …
