can an individual develop natural immunity against hepatitis b without being vaccinated?

Answer 1

Yes, by getting acute hepatitis B and recovering from it.

Answer 2

Acquired immunity may be obtained by natural or artificial means. In addition to this, acquired immunity may be either active or passive. A natural immunity is an acquired immunity which would suggest a past exposure (active) or a history of vaccination (passive). If your doctor has also told you that your hep B titers are sufficient, than you are considered immune for as long as your titers remain that way.