Hi, My Son Who Is 12 Years Old Has A

Hi, my son who is 12 years old has a plantar wart that has been treated by the dermatologist 7 times and had become smaller but still there. it is painful for him, and he is not willing to go anymore. The last cream she prescribe to him was zyclara, that I will start the treatment today. Do you have any other suggestions? is he low in his Immune system? How can I cure that and how I can prevent that? Thank you very much