What is the ruling of Islamic law on vaccinating children for immunity, especially with evidence suggesting potential harm?

There is no harm in seeking treatment before the onset of a disease if its occurrence is feared. This is known as vaccination because it falls under the category of repelling affliction before it occurs, as stated in the Hadith (definition): "Whoever eats seven dates of Medina in the morning will not be harmed by magic or poison." As for the temporary harm resulting from some vaccinations, it is overlooked when compared to the greater evil it repels, which is deadly diseases. This is similar to the slight pain experienced during the circumcision of boys, which is minor compared to the religious and worldly benefits. The lesser of two evils is committed to avert the greater. However, if it is medically proven that certain vaccinations cause greater harm than the diseases they prevent, then their use is impermissible, due to the Prophet's (peace be upon him) saying: "There should be no harm nor reciprocating harm."