• Christopher L Gilbert, Stephanie O Klopfer, Jason C Martin, Florian P Schödel, and Prakash K Bhuyan.
• Merck Sharp & Dohme Corporation, Whitehouse Station, NJ, USA. christopher_gilbert@merck.com
• Hum Vaccin. 2011 Dec 1; 7 (12): 1336-42.

BackgroundGenerating protective immune responses in older adults (particularly ≥65 y) remains challenging for vaccines in general. This study examined the immune response engendered in older adults by RECOMBIVAX HB™ manufactured using a modified adjuvant (modified-process hepatitis B vaccine; mpHBV), RECOMBIVAX-HB™, and ENGERIX-B™.MethodsRandomized, double-blind, multicenter study enrolled healthy, seronegative subjects (N=538) to receive mpHBV (10 µg hepatitis B surface antigen [HBsAg]), RECOMBIVAX-HB™ (10 µg HBsAg), or ENGERIX-B™ (20 µg HBsAg) at Day 1, Month 1, and Month 6. Prespecified analysis of subpopulations 50-64 y and ≥65 y was conducted. Serum antibody to HBsAg (anti-HBs) was measured Predose 1 and 1 mo Postdose 3.ResultsFor subjects ≥50 y, seroprotection rates (SPR, anti-HBs titer ≥10 mIU/mL) were 75.7% (95% CI: 68.0,82.2) for mpHBV, 68.0% (95% CI: 59.8,75.5) for RECOMBIVAX HB™, and 84.0% (95% CI: 77.0,89.6) for ENGERIX-B™. For subjects 50-64 y, SPRs were 82.1% (95% CI: 73.8,88.7) for mpHBV, 77.4% (95% CI: 68.7,84.7) for RECOMBIVAX-HB™, and 88.5% (95% CI: 81.1,93.7) for ENGERIX-B™. For subjects ≥65 y, SPRs were 57.5% (95% CI: 40.9,73.0) for mpHBV, 34.4% (95% CI: 18.6,53.2) for RECOMBIVAX-HB™, and 67.7% (95% CI: 48.6,83.3) for ENGERIX-B™. There were 6 non-vaccine related serious adverse events reported.ConclusionsThe majority of subjects ≥50 y old achieved seroprotection. The sub-population ≥65 y had lower vaccination responses than the 50-64 y sub-population. For subjects ≥65 y, mpHBV and ENGERIX-B™ groups achieved higher seroprotection rates than the RECOMBIVAX-HB group. The safety profile of mpHBV was consistent with the other groups.

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