Revaccination With PNEUMOVAX(TM) 23 in Older Adults (V110-007): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Revaccination With PNEUMOVAX(TM) 23 in Older Adults (V110-007) (NCT00560950), a non-randomized phase 3 study. The primary outcome is Geometric Mean Concentration for Prevaccination (Day 1) to Postvaccination (Day 30) During the Extension Phase Subjects Completing the Extension for Serotype 3.

2. Clinical Question

The study’s stated purpose was to assess whether revaccination was well tolerated and produced an immune response in older adults. The primary endpoint focuses on an antibody measurement, not on clinical illness or prevention of pneumococcal infection. Its title specifies the serotype 3 geometric mean concentration from prevaccination to postvaccination during the extension phase. The broader measurement description says antibody levels were assessed for eight pneumococcal polysaccharide serotypes by ELISA.

The comparison of the two listed groups should not be read as a randomized treatment comparison. The registry identifies the allocation as non-randomized and explicitly notes that the arms are not a like-for-like control comparison. Group differences could therefore reflect differences between the groups as well as differences associated with their revaccination histories. Details of those histories and the criteria used to assign participants to groups are not reported in the registry record.

3. Trial Design

This completed Phase 3 study is titled “Revaccination With PNEUMOVAX(TM) 23 in Older Adults (V110-007).” The official title describes a multicenter, open-label study of the safety, tolerability, and immunogenicity of revaccination. The registry lists non-randomized allocation, no masking, and a parallel model. Enrollment is recorded as 143. The study start is listed as 2007-07, and primary completion as 2008-05.

The intervention is pneumococcal 23v polysaccharide vaccine. The registry names a 1st Revaccination Group and a 2nd Revaccination Group, but their arm descriptions are blank. The meaning of the group labels, including the precise interval or history distinguishing the groups, is not reported in the registry record. The arms should not be treated as randomized alternatives: the record explicitly says they are not a like-for-like control comparison.

Open-label means the study was not masked, as also indicated by the registry’s masking field. Non-randomized allocation means the registry does not describe random assignment to the groups. In general, those design features matter when interpreting group comparisons: lack of random assignment can leave group differences entangled with characteristics that were not measured or adjusted for, and lack of masking can influence how outcomes are assessed or reported. Whether any such influences occurred in this study cannot be determined from the registry record.

The registry lists eight outcome measures and zero analyses. It does not report the detailed protocol, participant eligibility criteria, recruitment setting beyond the multicenter description, group assignment process, or the statistical analysis plan. The record gives no explanation of the enrollment target or sample-size justification. Those omissions limit reconstruction of how the study was conducted and how its outcomes were intended to be analyzed.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Base trial 4/97-4/98 Prior to results posted Initial: subjects received 1st or 2nd dose of PN23 Persistence: followed immune response 5 yrs; ended 4/03 Extension 7/07-4/08: enrolled 9-10 yrs after base. 1dose of PN23 Blood drawn Days 1\&30, immune response to 8 serotypes measured 143 of 400 enrolled: difficulty enrolling eligible/interested subjects

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All eligible participants

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Geometric Mean Concentration for Prevaccination (Day 1) to Postvaccination (Day 30) During the Extension Phase Subjects Completing the Extension for Serotype 3, measured over Day 1 & Day 30.

The primary endpoint is the geometric mean concentration of antibody to pneumococcal serotype 3, measured at Day 1 and Day 30 during the extension phase. The endpoint title refers to subjects completing the extension. The listed population is “All eligible participants,” so the registry record does not clarify how this population label corresponds to the endpoint title’s completion criterion.

Blood drawn at the two stated time points was used to measure IgG antibody levels by ELISA. The description says the assay covered eight pneumococcal polysaccharide serotypes: 3, 4, 6B, 8, 9V, 12F, 14, and 23F. The primary endpoint is specifically identified as serotype 3, rather than a combined measure across all serotypes. Its unit is gpELISA units/mL, and its dispersion is described as a 95% confidence interval.

In general, a geometric mean is useful for measurements that are positive and may vary multiplicatively: it summarizes values on a logarithmic scale and expresses the result back on the original scale. A confidence interval conveys uncertainty around an estimated mean; it is not a range intended to contain every participant’s measurement. The registry record contains no numerical geometric means or confidence limits, so neither the estimated antibody level nor its precision can be assessed from the record. Antibody concentration is a laboratory outcome and is not, by itself, a clinical outcome such as infection incidence.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the geometric mean summarize?

The primary endpoint uses a geometric mean concentration. In general, this is calculated by taking logarithms of the individual measurements, averaging on that transformed scale, and converting the average back to the original measurement scale. It can be appropriate for positive biological measurements whose variation is better understood proportionally than as equal absolute increments. The endpoint’s reported unit is gpELISA units/mL. The registry record does not give the underlying participant measurements or the numerical geometric mean.

A geometric mean describes a group-level average; it does not show the distribution of individual antibody concentrations. Participants may have values above or below the mean, and the mean alone cannot describe that spread. The registry identifies a 95% confidence interval as the endpoint’s dispersion measure, but no confidence limits are reported. The record also does not specify whether the interval was calculated on the logarithmic scale and then back-transformed, although that is a general approach for intervals around geometric means.

What does the confidence interval communicate?

In general, a confidence interval expresses the uncertainty associated with an estimated quantity under the assumptions of the analysis. It is not a statement that a fixed proportion of individual observations lies within the interval. Nor does the interval alone establish whether an observed difference is important. Interpretation depends on the estimate, interval, study question, and analysis plan. Here, the endpoint specifies a 95% confidence interval, but the interval’s bounds and the point estimates are not reported in the registry record. Its precision therefore cannot be judged.

The endpoint description gives two measurement times: Day 1 and Day 30. It does not report whether the primary analysis was a direct comparison of the two geometric means, a ratio, a transformed-scale difference, or another summary. No change estimate, test statistic, or p-value is reported. Those analysis details should not be inferred from the wording of the endpoint title.

Why does the allocation matter?

The registry describes allocation as non-randomized and lists parallel groups. In general, a parallel design follows separate groups under their assigned study conditions rather than having each participant receive every condition. Randomization is a method for assigning participants that can reduce systematic baseline differences between groups. Because this study is listed as non-randomized, the registry’s caution that the groups are not a like-for-like control comparison is important. Comparisons between them cannot automatically be interpreted as effects caused by revaccination.

Open-label status means treatment assignment was not masked, consistent with the registry’s masking entry of none. In general, lack of masking can affect behavior, reporting, or assessment, depending on the outcome and how it is collected. The primary outcome is an antibody measurement by ELISA, but the record does not describe laboratory blinding, assay procedures in detail, or safeguards against measurement bias. No claim about the presence or absence of bias can be made from that omission.

What can be inferred from the planning assumptions?

The record describes assumptions for planning illustrations based on an observed effect: two-sided significance level 0.05, equal allocation between the two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not a description of the study’s original design justification. The calculation results and the effect used for those illustrations are not reported in the registry record. They cannot be used to claim that the study had a particular probability of detecting an effect, and sample-size planning illustrations are not observed power.

In general, a sample-size calculation estimates how many participants may be needed to detect a specified effect under assumptions about variability, significance level, allocation, and analysis. A calculation based on an effect observed in the same study is especially dependent on that estimated effect and does not replace a prospective design rationale. The registry does not report the protocol’s original assumptions, target enrollment justification, or whether any planned sample-size calculation was performed.

The stated planning method uses a normal approximation. In general, such approximations rely on the sampling behavior being adequately represented by the assumed distribution. The registry record does not describe checks of those assumptions for the calculations. It also does not provide any recalculated estimates for the primary endpoint, and there is no sponsor analysis result in the listed details against which to assess a recalculation.

What is missing about the analysis?

The registry lists zero analyses. It does not report an analysis plan, model, covariate adjustments, hypothesis tests, multiplicity procedures, or methods for handling measurements that were unavailable. It also does not say whether the analysis used all eligible participants, only participants completing the extension, or another population. This matters because the endpoint title and population field use different descriptions. Without the analytic population and handling rules, the intended denominator and the treatment of incomplete observations are unclear.

In general, an analysis plan specifies how measurements will be summarized and compared, which participants contribute to each result, and how uncertainty and missing data are handled. These choices can affect estimates and their precision. The registry record provides the endpoint’s measure, time points, unit, and confidence-interval description, but not enough detail to reproduce or evaluate an analysis. No numerical result should be reconstructed from the design information alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists eight outcome measures, but the statistical relationship among them is not reported. In particular, it does not identify a multiplicity adjustment, a hierarchy of outcomes, or whether any outcomes were considered exploratory. In general, when multiple outcomes or comparisons are examined, the chance of finding an apparently unusual result can increase unless the analysis plan accounts for the number and structure of tests. Whether that issue applied to the study’s reported analyses cannot be assessed because the registry lists zero analyses and gives no results or testing plan.

Missing-data handling is also not reported in the registry record. The primary endpoint title refers to subjects completing the extension, while the population field says all eligible participants. The record does not explain whether participants without a Day 30 measurement were excluded, how incomplete measurements were handled, or whether the analysis population differed across outcomes. It also does not describe reasons for missing measurements or participant flow by group.

These details affect interpretation. In general, analyzing only participants with complete measurements can produce a biased estimate if completion is related to the outcome or participant characteristics. Other approaches also require assumptions, which should be stated and assessed. No specific approach or assumption can be attributed to this study based on the registry record.

The record does not report an intention-to-treat population, a per-protocol population, imputation, sensitivity analyses, or rules for excluding observations. It also does not explain whether all eligible participants were included in safety summaries or whether the reported safety denominators applied throughout follow-up. Consequently, neither the completeness of the endpoint analysis nor the robustness of any estimate can be evaluated from the available registry information.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse event figures list 71 participants at risk in each group and zero affected by serious adverse events in each group. The record’s serious-event terms list is empty. This means the registry lists no participants affected in those serious-event fields; it should not be read as proof that no adverse events occurred or that the study established the absence of risk.

For other adverse events, the record lists 48 affected in the 1st Revaccination Group and 60 in the 2nd Revaccination Group. The at-risk denominators for this category are not reported in the registry record. Without those denominators, the counts cannot be interpreted as comparable rates. The registry also does not report the event definitions, severity breakdown, duration, or attribution for these other adverse events.

Deaths are not reported in the registry record. The group comparison is non-randomized, and the registry cautions that the arms are not a like-for-like control comparison. The posted counts therefore describe the listed safety fields, not a causal comparison between groups.

12. What the Result Does, and Does Not, Mean

The registry record establishes that the study was designed to examine revaccination with pneumococcal 23v polysaccharide vaccine in older adults and that the primary endpoint concerned serotype 3 antibody concentration at Day 1 and Day 30 during the extension phase. It also identifies an ELISA measurement across eight serotypes in the broader outcome description. These are descriptions of what was measured, not results showing what the measurements were.

No numerical primary endpoint results, confidence limits, or statistical analyses are reported. The record therefore does not show whether antibody concentrations increased, decreased, or stayed similar over the stated period, nor how precisely any estimate was measured. It also does not provide clinical infection outcomes that would support conclusions about prevention of illness. The study’s stated purpose is not a substitute for the results.

The safety entries show zero participants affected by serious adverse events in each group, with 71 at risk in each. Other adverse events are listed for both groups, but the corresponding at-risk denominators are not reported. Deaths are not reported in the registry record. These entries are limited summaries and do not provide event descriptions or enough information for a complete comparative safety assessment.

The two groups were not randomly assigned, and the registry explicitly cautions against treating them as like-for-like controls. Any apparent group differences would need to be interpreted in light of that design and the missing information about group histories, baseline characteristics, and analysis methods. The registry record does not provide adjusted estimates that might address measured differences, and even such adjustment would not by itself guarantee comparability.

In general, a study’s design and endpoint help identify the question it set out to address, while its results and analysis determine what can be concluded from the observations. Here, the design and measurement descriptions are available, but the numerical outcome results and statistical analysis are not reported. The record can support a careful account of study structure and selected safety counts; it cannot support a conclusion about the size of an antibody response, the comparative effect of the groups, or the clinical consequences of revaccination.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between an outcome definition and an outcome result. The registry names a quantitative antibody endpoint, its unit, measurement method, time points, and confidence-interval type. Those details clarify what was intended to be measured. Without the numerical estimates and their uncertainty, however, the endpoint cannot answer how much antibody was measured or how the values changed over time.

The study also illustrates why allocation matters. The registry identifies a non-randomized design and warns that its groups are not a like-for-like control comparison. A group label alone does not establish exchangeability: participants may differ for reasons associated with group assignment. Statistical comparisons in such settings need careful design information and transparent adjustment methods, neither of which is reported in the registry record.

The distinction between antibody measurements and clinical outcomes is also important. In general, a laboratory immune measure can describe a biological response, but it is not automatically equivalent to evidence about clinical illness. The primary endpoint is an antibody concentration; the registry record does not report a clinical infection result.

Finally, the record shows how incomplete analysis reporting can limit interpretation even when an endpoint is precisely named. The analysis population is unclear from the different population descriptions, and the registry does not describe missing-data methods, multiplicity handling, or the statistical plan. Such details are necessary for assessing bias, precision, and the scope of conclusions. The record’s value is therefore chiefly in documenting the design and measurement framework, while its missing results and methods leave substantial uncertainty about what the study observed.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary limitation is that numerical results for the primary endpoint are not reported in the registry record. There are no geometric mean concentrations, confidence limits, or analysis results to interpret. The record also lists eight outcome measures but provides no outcome values in the registry record for this analysis.

The endpoint title refers to subjects completing the extension, whereas the population field says all eligible participants. The registry does not resolve this difference or define the analysis population. It also does not report participant flow, missing measurement counts, reasons for non-completion, or methods for handling missing data.

The study is non-randomized and open-label. The registry explicitly states that the groups are not a like-for-like control comparison. Arm descriptions are blank, so the group labels do not explain the revaccination histories or other characteristics that distinguish them. Baseline characteristics, group assignment criteria, and adjusted analyses are not reported in the registry record.

The safety information is limited: serious-event counts are listed, but serious-event terms are not; other adverse event counts have no reported at-risk denominators; and deaths are not reported in the registry record. Event definitions and follow-up details are also not reported.

The registry lists zero analyses and does not describe the statistical plan, multiplicity procedures, or sample-size justification. Although planning assumptions are described, the calculation results and original design rationale are not reported. These gaps prevent evaluation of the intended analysis, the precision of results, and the robustness of any conclusions.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Revaccination With PNEUMOVAX(TM) 23 in Older Adults (V110-007) — NCT00560950.
• Registry record last updated 2017-04-11; status last verified 2017-03.
• Results first posted 2009-05-25.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT00560950 is a completed Phase 3, multicenter, open-label, non-randomized parallel study sponsored by Merck Sharp & Dohme LLC. It examined revaccination with pneumococcal 23v polysaccharide vaccine in older adults. Enrollment is listed as 143; the study start is 2007-07 and primary completion is 2008-05.

The primary endpoint is the geometric mean concentration of serotype 3 antibody at Day 1 and Day 30 during the extension phase, with a 95% confidence interval. The broader description says ELISA was used to measure IgG levels for eight serotypes. Numerical endpoint results and analyses are not reported in the registry record.

The record lists two non-randomized groups and cautions that they are not like-for-like controls. Serious adverse events are listed as affecting zero participants in each group, with 71 at risk per group. Other adverse event counts are 48 and 60, without reported denominators for that category. Deaths are not reported in the registry record.