In this work we present VaccineHero, an eXtended Reality system that aims to reduce children’s discomfort during vaccination. In our proposal the child wears a headset during vaccination and watches a short story in VR. The story includes a hero touching the child’s arm and the doctor synchronises the insertion of the needle with the VR content, so that the child is distracted efficiently. A clinical trial has been carried out, involving 2 doctors and a cohort of 16 children, and has shown that the use of VaccineHero reduces children’s discomfort during vaccination by a staggering 40% and totally eliminates extreme discomfort. The implemented solution is extremely affordable, as it can be deployed on simple headsets or even Cardboard devices, a feature that makes it a realistic option for any paediatric practice. It can also be extended to support other medical activities that involve needles, such as blood draw and blood donation.