If your test results are low, your doctor may recommend a booster shot or a repeat of the series. If you confirm you completed the vaccine series, you can get a booster dose of the vaccine. Your surface antibody level will be tested again 1 or 2 months after the booster. If the blood test result is greater than 10, then you are protected and will not require an additional booster shot in the future. (Ongoing studies show continued immunity for 30 years) If a booster shot does not result in a level greater than 10, then complete the remaining two doses of the vaccine series and recheck the levels again after 1-2 months. Retain a copy of the titer test as proof of immunity.