Other places you may be able to volunteer to get some medicine adjacent experience–
summer camps for disabled or autistic children, Special Olympics, local group homes for disabled adults, any kind of special program offered for disabled or autistic children (like therapeutic horseback riding or therapeutic swimming programs), adult daycare programs for the elderly w/ dementia, nursing home aide.
Some hospitals will allow 16 and up to volunteer with Child’s Life programs for in-patient pediatric patients. (My younger D did this one summer.)
Some hospitals offer summer programs for rising high school seniors that have them shadow various different healthcare professions (physician, nurse, physical therapist, clinical lab scientist, audiologist, etc) Your HS counselor may know if any of your local hospitals have a program like this. OR, you can check for yourself by calling the volunteer coordinator at your local hospitals and asking.