An employee thinks she had 3 doses of hepatitis B vaccine in the past but has no documentation of receiving those doses. Before reading the recommendations to revaccinate her, we obtained an anti-HBs titer and the result was greater than 10 mIU/mL. With this lab result, can’t we assume she is immune?

No. A positive anti-HBs indicates that the vaccinated person is immune at the time the person was tested but does not assure that the person has long-term immunity. Long-term immunity has been demonstrated only for people attaining an adequate anti-HBs result of at least 10 mIU/mL after completing a full vaccination series. The most direct way to deal with this is to vaccinate the employee with a series of hepatitis B vaccine; test for anti-HBs in 1–2 months and document the result in the employee’s health record. An adequate anti-HBs result from a documented vaccine series would assure not only seroprotection, but long-term protection.