Which are the side effects of flu vaccine in 11 month old baby, he is on warfarin, aspirin and propranolol becouse of aneurysms in coronary arteries?

Minor discomforts. Fever and local pain over the injection site are the common side effects. Since your infant is on chronic Aspirin therapy, annual influenza vaccination is essential. Reye syndrome has been known to occur to children who take Aspirin while they are having flu (influenza).
Should be none. There are no specific problems with the flu vaccine in this setting. Obviously a shot in anyone on Coumadin (warfarin) may cause a bit of a bruise at the injection site.