I received the vaccine years ago—am I still immune?

If it has been years since you have been vaccinated, you may need or may request an HBV surface antibody blood test to confirm that you are still protected. A person is considered protected if they have a positive anti-HBs or HBsAb test result greater than 10 mIU/mL. Sometimes these test results are under 10 and there is concern whether these low levels will still provide protection against HBV. Anti-HBs or HBsAb test results can decrease over time, but an individual can still be protected even if the test results are less than 10.