664. A Phase 3, Open-label, Follow-up Trial Evaluating the Safety and Immunogenicity of a Subsequent Dose of 13-Valent Pneumococcal Conjugate Vaccine (PCV13) in Elderly Adults who Received PCV13 Followed by 23-Valent Pneumococcal Polysaccharide Vaccine (PPSV23) in a Prior Trial
Session: Poster Abstract Session: Pneumococcal Vaccines
Friday, October 21, 2011
Room: Poster Hall B1
Background: A 13-valent pneumococcal conjugate vaccine (PCV13) is currently being developed for adults. Previous studies have demonstrated a reduced anti-pneumococcal immune response when pneumococcal vaccines are administered after the licensed, unconjugated 23-valent pneumococcal polysaccharide vaccine (PPSV23). The purpose of this trial was to assess whether this effect is also observed in adults who initially were administered the conjugated PCV13 vaccine prior to receipt of PPSV23.  Hence, these adults received a second administration of PCV13 one year after PPSV23 and the resulting immune responses were assessed. 

Methods: Adults aged ≥65 years who received PCV13 then PPSV23 in a prior study received a subsequent dose of PCV13. The sequential PCV13/PPSV23/PCV13 vaccinations were given at 1-year intervals. Immune responses 1 month after each vaccination, as measured by opsonophagocytic assay (OPA), were compared. Adverse events were also assessed.  

Results: The evaluable immunogenicity population included 98 adults (46.9% male; mean age 70.7 years). OPA geometric mean titers (GMTs) for 12 of 13 serotypes were lower after the PCV13/PPSV23/PCV13 series compared to responses after the initial PCV13 administration. GM fold rise (GMFRs) were <1.0 for 12 serotypes; 10 serotypes showed a statistically significantly lower response after PCV13/PPSV23/PCV13 relative to PCV13 (upper limit of 95% CI for GMFR <1.0).  

In addition, OPA GMTs for 10 of 13 serotypes were lower after the PCV13/PPSV23/PCV13 series compared to responses after PCV13/PPSV23. GMFRs were <1.0 for 10 serotypes. Eight serotypes showed a significantly lower response after PCV13/PPSV23/PCV13 relative to PCV13/PPSV23 (upper limit of 95% CI for GMFR <1.0).

Reactogenicity was comparable; there were no related serious adverse events.

Conclusion: Administration of an initial dose of the PCV13 conjugated vaccine did not prevent the reduced immune responses to a subsequent dose of PCV13 given after the PPSV23 free polysaccharide vaccine in the vaccine sequence PCV13/PPSV23/PCV13. 


Subject Category: I. Adult and Pediatric Vaccines

Christine Juergens, MD1, Pierre de Villiers, PhD2, Keymanthri Moodley, MBChB, DPhil2, Deepthi Jayawardene, MS3, Kathrin U. Jansen, PhD4, Daniel A Scott, MD4, Emilio A. Emini, MD3, William Gruber, MD4 and Beate Schmoele-Thoma, MD1, (1)Pfizer Vaccine Research, Berlin, Germany, (2)University of Stellenbosch, Tygerberg, South Africa, (3)Pfizer Inc, Collegeville, PA, (4)Pfizer Vaccines Research, Pfizer Inc, Pearl River, NY

Disclosures:

C. Juergens, Pfizer: Employee, Salary

P. de Villiers, Wyeth Vaccines Research: Research Contractor, Research grant

K. Moodley, Pfizer: Speaker on medical ethics, Speaker honorarium
Wyeth Vaccines Research: Investigator, Speaker honorarium

D. Jayawardene, Pfizer: Employee and Shareholder, Salary

K. U. Jansen, Pfizer: Employee and Shareholder, Salary

D. A. Scott, Pfizer: Employee and Shareholder, Salary

E. A. Emini, Pfizer: Employee and Shareholder, Salary

W. Gruber, Pfizer: Employee and Shareholder, Salary

B. Schmoele-Thoma, Pfizer: Employee and Shareholder, Salary

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.