Kawasaki disease (KD) is an acute febrile systemic vasculitis most commonly seen in children under the age of 5 years old. This trial has been designed as a multi-center, prospective, randomized controlled, evaluator-blinded trial with two parallel groups to determine whether IVIG alone as the primary therapy in acute-stage KD is as effective as IVIG combined with high-dose aspirin therapy. The primary endpoint is defined as CAL formation at 6-8 weeks.