thank you for posting your query in healthcaremagic.com... firstly, anti-HBs can be positive in many cases...like seroconversion, hbv infection in the recent past, distant past, vaccination or even false positive... if only the anti-HBs is positive and the rest of the serological markers are negative, then it is highly indicative of immunization with HBsAg after vaccination.... also you give a history of receiving the last booster of HepB vaccination so it is likely that the seromarkers indicate that immunisation only.... and as far as medical clearance is concerned, it wont be of any problem...you should get clearance in work definitely.... hope this was helpful... you can come to me for any further questions.... regards