Long-term protection following a primary series of hepatitis B vaccine in Alaska Native children and adults

BACKGROUND: Vaccination is effective at preventing chronic HBV infection and its complications, but the duration of protection and need for booster doses have not been determined. METHODS: We administered a 3-dose primary series of plasma-derived hepatitis B vaccine to Alaska Native persons aged 6 months or above who resided in an HBV-endemic area of western Alaska. Persons with antibody to hepatitis B surface antigen (anti-HBs) ≥10 milli-international units per milliliter (mIU/mL) at 6 months after series completion were followed through 41 years after vaccination. Beginning at 22 years, participants with anti-HBs <10 mIU/mL were offered a booster dose (ie, challenge dose) of recombinant hepatitis B vaccine and retested 4 weeks later as a surrogate for immune memory. Combining these immune-memory data with a survival model estimating anti-HBs persistence, we estimated the overall proportion with serologic evidence of protection at 22, 30, 35, and 41 years. We also described breakthrough hepatitis B infections. RESULTS: During 1981-1982, 1351 persons completed the hepatitis B vaccine primary series and had anti-HBs ≥10 mIU/mL at 6 months after vaccination; median age at enrollment was 13 years (range: 0.5-77). The overall proportion with serologic evidence of protection was 95% at 22 years, 95% at 30 years, 88% at 35 years, and 91% at 41 years after vaccination. At 41 years, 32% had circulating anti-HBs ≥10 mIU/mL, and 59% had immune memory. During 41 years of follow-up, 16 (1%) persons had evidence of a breakthrough infection; none developed chronic hepatitis B. CONCLUSIONS: We found serologic evidence of protection among Alaska Native persons 41 years after primary hepatitis B vaccination. Our findings support the recommendation that booster doses are not needed in endemic areas.