The Hepatitis B Surface Antibody (anti-HBs) is the most common test. Its presence will indicate previous exposure to HBV, but the virus is no longer present and the person cannot pass virus on to others. The antibody will also protect the body from future HBV infection. In addition to exposure to HBV, these antibodies can also be acquired from successful vaccination. This test is peformed to determine the need for vaccination (if anti-HBs is absent), or following the completion of vaccination against the disease, or following an active infection.