Evaluation of the response to a booster dose of hepatitis B vaccine in previously immunized healthcare workers.

INTRODUCTION: Hepatitis B vaccination is recommended for all healthcare workers (HCW) at risk of exposure to infectious body fluids. However, the absolute duration of protection from immunization is unknown. The purpose of this randomized comparison trial was to determine how previously immunized HCW respond to different booster doses of hepatitis B vaccine. METHOD: Adult HCW (n=59) were classified by level of hepatitis B surface antigen (anti-HBs), either <10 milli-International Units per milliliter (mIU/ml) or 10-50 mIU/ml. Participants were then randomized to receive a 2.5 or 10 microg dose of hepatitis B vaccine. Evaluation of anti-HBs levels were conducted 10 to 14 days, one month and one year postbooster. RESULTS AND DISCUSSION: All participants responded to the booster dose with increased anti-HBs levels. At 14 days, mean anti-HBs levels were significantly higher for those with higher levels at baseline (P=0.004) and those receiving the 10 microg dose (P=0.016). At one month, those with higher anti-HBs levels at baseline and those receiving the 10 microg dose were significantly higher (P<0.01 for both). At one year, the increase for the higher dose was no longer statistically significant when examined by itself (P=0.081); statistical significance (P=0.021) was achieved after adjusting for anti-HBs level at baseline. For all participants, the geometric mean anti-HBs level was 2618 mIU/ml at 14 days, 2175 mIU/ml at one month and 88.9 mIU/ml at one year. At all time points the increase in anti-HBs levels represented an increase over the geometric mean baseline level of anti-HBs (7.4 mIU/ml). Hepatitis B immunized adults responded to a booster dose of hepatitis B vaccine from 3 to 13 yr postvaccination series. Data support current recommendations that immunized HCW do not require periodic antibody testing or vaccine boosters.