The quantity of Anti-Hbs do decrease over time, especially when the body is not exposed to the virus all that time. If you are in high risk category for hbv infection, you can consider a booster injection of the hbv vaccine to bring the number up again. Consult your doctor.
Hi,
5 years ago I had my Hepa B vaccine and checked Anti-HBs with 5.98 value last 2007. But when I checked it now, it's only 1.436. Why does it become lower? If I'll have 3 doses of Hepa B (Engerix B) Vaccine again which will be given in rapid doses, will it become higher up to the protective value of >10?
Yours is a qualitative test. Usually a quantity of HBsAb > 10mIU/ml is considered to be protective.