Benefits of the DTaP vaccine Saves lives. Protects young children from serious disease. Side effects of the DTaP vaccine The most common side effects are usually mild and occur in about 1 out of 4 children. They include - Swelling, and pain from the shot, Fever, Vomiting. A fever over 105 degrees occurs in 1 out of 16,000 children. Nonstop crying for 3 hours or more occurs in about 1 out of 1,000 children. Seizures (jerking or staring) occur in about 1 out of 14,000 children.The seizures do not cause long-term harm. Serious reaction to the DTaP vaccine occurs in less than 1 in a million children.