title: Safety and immunogenicity of a modified process hepatitis B vaccine in healthy adults ≥50 years.
abstract: BACKGROUND
  Generating 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™.
  
  
  METHODS
  Randomized, 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.
  
  
  RESULTS
  For 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Merck Sharp & Dohme Corporation, Whitehouse Station, NJ, USA. christopher_gilbert@merck.com
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Gilbert
authors.forename: Stephanie O
authors.initials: SO
authors.lastname: Klopfer
authors.forename: Jason C
authors.initials: JC
authors.lastname: Martin
authors.forename: Florian P
authors.initials: FP
authors.lastname: Schödel
authors.forename: Prakash K
authors.initials: PK
authors.lastname: Bhuyan
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000009:adverse effects; D000368:Aged; D000369:Aged, 80 and over; D004311:Double-Blind Method; D005260:Female; D006509:Hepatitis B / Q000276:immunology / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood*; D006514:Hepatitis B Surface Antigens / Q000008:administration & dosage / Q000276:immunology; D017325:Hepatitis B Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; C075654:Engerix-B; D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines; C075655:Recombivax HB; D014614:Vaccines, Synthetic