I have a fear of suddenly developing meningitis or having a brain tumour. are these rare? i have bad anxiety.

Both are rare: There is a vaccine that will definitely help protect against bacterial meningitis, but it is still rare even without this new advancement. Brain tumors are also exceedingly rare. It is important to find somebody to talk to about your anxiety/fears, be it a parent, other family member, guidance counselor or social worker, life coach or mental health professional. No shame in feeling this way.