Drugmaker AstraZeneca has removed a study group comprising children from a trial of its COVID-19 vaccine candidate in Britain, clinical trial registers in the United States showed on Monday.

The mid-to-late stage trial of more than 12,000 participants previously included children above the age of five years with the consent of their parents. However, the page was updated on Dec. 10 to reflect the changes.

AstraZeneca, which is developing the vaccine along with the University of Oxford, did not immediately respond to a request for comment.