Some children have been harmed by vaccinations.  Some children have been harmed by almost anything that happens under the sun.  However the real comparison is how many children died of the diseases before vaccinations were available compared to how many after.  The number of children seriously harmed by vaccinations is a minute fraction of those that were harmed by the diseases.  I know that is of no comfort to a parent whose child is harmed but I would rather take the rather paltry risk that my children could be harmed by vaccination than the much more substantial risk all children faced prior to vaccinations.  If you are weighing the risks, talk to someone over the age of 70.  Everyone I know of in that age range can tell me of a sibling, cousin or childhood friend who was seriously harmed or more often died of one the diseases that is now mostly eradicated due to cleaner water sources, better hygiene and vaccinations.