Small pox eradication is evidence of the importance of immunization. Small pox killed more people than any other pathogen in history. It was highly contagious and deadly and was spread throughout the world up until the 20th century. Once the vaccine was discovered and used it has been completely eradicated to the point you don’t even need to vaccinate for it anymore. This shows how important immunizations are regardless of risk.
Unimmunised children are a risk to others. The argument that your unvaccinated child is not a risk to anyone but himself because other kids will be vaccinated is incorrect. There are some children with conditions that don’t allow vaccination and the more other kids without immunisation the greater risk of a spread of disease.