Objective: To determine whether a difference in antibody to hepatitis B surface antigen (anti-HBs) response to a hepatitis B vaccine challenge dose existed among persons with a baseline anti-HBs level of 0 mIU/mL (group 1) and those with "non-zero" levels of 0.1-4.9 (group 2) and 5.0-9.9 (group 3) mIU/mL, according to the VITROS ECi anti-HBs assay.
Design: Subanalysis of randomized clinical trial. Response was defined as a postchallenge anti-HBs level of at least 10 mIU/mL and 4-fold rise in anti-HBs level 2 weeks after a single challenge dose of 10 vs 20 µg Engerix-B. Baseline was defined as the anti-HBs level immediately before administration of the challenge dose.
Setting: Pediatric integrated healthcare system near Houston, Texas.
Participants: Three hundred nineteen US-born 16-19-year-olds who completed the hepatitis B vaccine series during the first year of life.
Results: One hundred seventy-eight persons had zero (group 1) and 141 (114 group 2 and 27 group 3) had non-zero anti-HBs levels at baseline. Response to the challenge dose was significantly higher among those with non-zero vs zero anti-HBs levels, irrespective of challenge dosage; only 1 person with a non-zero anti-HBs level failed to respond to the challenge dose (group 3, 27/27 [100%] vs group 2, 113/114 [99%] vs group 1, 145/178 [82%]; P<.0001).
Conclusions: Among participants with residual anti-HBs levels less than 10 mIU/mL 16-19 years after primary hepatitis B vaccination during infancy, non-zero anti-HBs levels, with rare exception, indicated persistence of immune memory to HBsAg.
Trial registration: ClinicalTrials.gov Identifier: NCT01341275