PCV13 and PPSV23 Administration: Does the Order Affect Immune Response?

Two sequential administration groups were compared by demonstrating the antibody response curve and the reverse cumulative distribution curve analyses by serotype.

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SAN DIEGO—When PCV13 and PPSV23 were sequentially given 1 year apart, the observed immune responses in older adults were higher than those of adults given PPSV23 followed by PCV13, according to Erica Chilson, PharmD, from Pfizer Inc., Collegeville, PA. 

Generally, clinical recommendations for pneumococcal immunization state using PCV13 first then PPSV23 after. This sequential administration is supported by reduced functional opsonophagocytic assay (OPA) titer data from patients who received PPSV23 first instead of PCV13 first. 

A previous Phase 3 study involving pneumococcal vaccine-naive adults aged 60–64 years administered PCV13 followed by PPSV23 one year later (PCV13/PPSV23) or PPSV23 followed by PCV13 one year later (PPSV23/PCV13). For this analysis, Dr. Chilson and colleagues compared the 2 sequential administration groups by demonstrating the antibody response curve analyses by serotype and the reverse cumulative distribution curve (RCDC) analysis by serotype. 

For both PCV13/PPSV23 and PPSV23/PCV13 groups, OPA titers rose significantly from pre-vaccination to 1 month post-initial vaccination. The OPA titers decreased over the 1-year interval between vaccinations for all serotypes “but remained higher at the pre-vaccination 2 time points compared to baseline for both groups,” noted Dr. Chilson. 

Regarding antibody response curves, the OPA geometric mean titers (GMTs) were typically higher for all shared serotypes across all measured time points in the PCV13/PPSV23 group vs. PPSV23/PCV13 group. The RCDC analyses data also showed that OPA titers after the second vaccination were generally higher with the PCV13/PPSV23 group across the full range of responses vs. PPSV23/PCV/13. 

“Although this study was not designed to determine the optimal interval between PCV13 and PPSV23 doses, it nonetheless provides insight into the immune response when the vaccines are given sequentially in older adults at an interval of one year later,” concluded Dr. Chilson. Findings from this analysis support the universal recommendation of giving PCV13 first when use of both pneumococcal vaccines is appropriate.

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Chilson, E. Sequential administration of PCV13 followed by PPSV23 results in a more robust immune response in PPSV23-naive adults age 60-64 years. Poster presented at IDWeek; October 4–8, 2017; San Diego, CA. http://www.idweek.org