The Power of a Band Aid

My 2-year-old niece, had some vaccinations. When she got home, she looked a down. Didn't want to play with her brother Or be touched by their parents. She was sitting in a corner, with a very sad face. Her mother worrying a bit. Checked her temperature, she was fine. She noticed her girl, was constantly looking at her arm. The mother decides to remove the Band-aid. Like a miracle, the smiles returned. She went back to playing. She was herself again. Who would know that a single Band-Aid, could have so much power?