> Serious adverse events are defined as: • Death; • A life-threatening adverse event; • Inpatient hospitalization or prolongation of existing hospitalization; • A persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions; • A congenital anomaly/birth defect; • An important medical event that based on appropriate medical judgement may jeopardize the individual and may require medical or surgical intervention to prevent one of the outcomes listed above.
It would not take very many such "serious adverse events" in a trial of 1100 before I'd argue that the vaccine is not safe for children.