Most vaccine side effects are not dangerous. Any medicine, including vaccines, can cause side effects. Most of the time, these side effects are minor. Some examples are a low-grade fever, headache, fussiness or soreness at the injection site.
Rarely, a child might experience a severe side effect, such as an allergic reaction or a seizure. These are rare side effects, and caregivers and health care providers monitor for them after vaccination.
Of course, vaccines aren't given to children who have known allergies to specific parts of the vaccine. And if your child has a life-threatening reaction to one vaccine, further doses of that vaccine won't be given.
The risk of a vaccine causing serious harm or death is very small. The benefits of getting a vaccine are much greater than the possible side effects for almost all children.