Program Schedule

LB-7
A Post-Hoc Assessment of Duration of Protection in CAPiTA (Community Acquired Pneumonia Immunization Trial in Adults)

Session: Oral Abstract Session: Late Breaker Oral Abstracts
Saturday, October 11, 2014: 11:30 AM
Room: The Pennsylvania Convention Center: 105-AB

Background:   In CAPiTA, PCV13 was effective in preventing vaccine-type pneumococcal community acquired pneumonia (VT-CAP) and vaccine-type invasive pneumococcal disease (IPD) in adults >65 years of age (n=84,496).  Vaccine efficacy (VE) was 46% for a first episode of VT-CAP (primary objective) and 45% for nonbacteremic/noninvasive (NB/NI) VT-CAP and 75% for a first episode of VT-IPD in the per-protocol population. The persistence of VE over time in CAPiTA has not been quantified.

Methods:   The observed accumulation of episodes for VT-CAP, NB/NI-VT-CAP, and VT-IPD over the course of the study following vaccination (3.97 years mean duration across subjects) was plotted.  To further study the pattern of efficacy over time, post hoc Kaplan-Meier time-to-event analyses (KM) of the primary and secondary endpoints were performed to study the potential effect of censoring.  Behavior of VE over time was also derived, and poisson regression (PR) was used to estimate the effects of treatment, time, and time by treatment interaction.   

Results:   Observed accumulation of episodes is shown in Figures 1-3. KM showed significant treatment effects for all endpoints (Log-Rank test p<0.05) in time to event confirming that the interpretation of the Figures 1-3 is not affected by censoring.  Table 1 shows the VE by year since vaccination for VT-CAP.  PR showed statistically significant treatment (p<0.05 for VT-CAP, NB/NI-VT-CAP, and VT-IPD, respectively) and time effects (p<0.05 for all endpoints but VT-IPD p>0.05) consistent with vaccine efficacy estimates and natural variation in observed disease incidence over time; however time by treatment interaction was not significant (p>0.05 for all endpoints) indicating that the pattern of protection remained stable over the time of observation.

Conclusion:   Prevention of VT-CAP, NB/NI-VT-CAP, and VT-IPD in CAPiTA began shortly after vaccination and persisted through the remainder of the study.  Waning of vaccine-type protection was not observed. 

                                                     

Table 1:  Vaccine Efficacy Estimates (p-values) for VT-CAP by Years since Vaccination

Endpoint

Years since Vaccination

Vaccine Efficacy (%)

p-value

VT-CAP

1

45.45%

0.1214

 

≤ 2

50.00%

0.0076

 

≤ 3

42.86%

0.0054

 

≤ 4

44.05%

0.0016

 

≤ 5

45.56%

0.0006

 

 (Funded by Pfizer, Inc.; ClinicalTrials.gov number NCT00744263.)

 

Scott D. Patterson, PhD1, Chris Webber, MD, PhD2, Wayne Drews3, Susanne M Huijts, MD4, Marieke Bolkenbaas, MD4, Diederick E. Grobbee, MD, PhD4, William C. Gruber, MD5, Daniel A. Scott, MD5, Marc JM Bonten, MD, PhD4 and The CAPiTA study team, (1)Pfizer Vaccine Research, Collegeville, PA, (2)Pfizer Vaccine Clinical Research, Maidenhead, United Kingdom, (3)inVentiv Health Clinical, LLC, Austin, TX, (4)Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands, (5)Pfizer Vaccine Research, Pearl River, NY

Disclosures:

S. D. Patterson, Pfizer: Employee and Shareholder, Salary

C. Webber, Pfizer, Ltd: Employee and Shareholder, Salary

W. Drews, inVentiv Health LLC: Employee, Salary

S. M. Huijts, None

M. Bolkenbaas, None

D. E. Grobbee, Pfizer: Collaborator and Research Contractor, Research grant

W. C. Gruber, Pfizer, Inc.: Employee and Shareholder, Salary and Stock and Stock options

D. A. Scott, Pfizer Vaccine Research: Employee and Shareholder, Salary and Stock, stock options

M. J. Bonten, Pfizer: Consultant, Consulting fee, Grant recipient and Research grant

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