Moderna expanding kids vaccine study to better assess safety Matthew Perrone And Linda A. Johnson Associated Press FILE - In this March 29, 2021 file photo, a worker readies syringes with the Moderna COVID-19 vaccine in Metairie, La. Moderna plans to expand the size of its study in younger children to better detect rare side effects. The company said Monday, July 26, 2021 it is in talks with the Food and Drug Administration to enroll more patients in its study of the vaccine in children under 12 years old and younger. (AP Photo/Gerald Herbert, File) (Copyright 2021 The Associated Press. All rights reserved.) WASHINGTON – Moderna said Monday it plans to expand the size of its COVID-19 vaccine study in younger children to better detect rare side effects, such as a type of heart inflammation recently flagged by U.S. health authorities.