Feasibility Study of GlaxoSmithKline Biologicals' GSK2202083A Vaccine in Healthy Infants at 3, 5 and 11 Months of Age.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility Study of GlaxoSmithKline Biologicals' GSK2202083A Vaccine in Healthy Infants at 3, 5 and 11 Months of Age. (NCT00871741), a randomized phase 2 study. The primary outcome is Anti-PRP Antibody Concentrations ≥ 0.15 mg/mL.

2. Clinical Question

The trial was designed to assess the safety and immunogenicity of GSK Biologicals’ GSK2202083A vaccine given as a three-dose course at 3, 5 and 11 months of age. It compared that course with Infanrix hexa given at the same ages and Menjugate given at 3 and 5 months. The central statistical question was whether the planned study could describe antibody responses and safety in the enrolled groups. The registry record says no blood samples were taken after termination, so the antibody question has no observed result.

Safety was also part of the study objective. The listed secondary outcomes concern solicited local and general symptoms, unsolicited adverse events, and serious adverse events. The posted counts therefore provide limited descriptive safety information, but they cannot answer the antibody-response question. The registry record does not report a reason for termination or a separate explanation of what prompted it.

3. Trial Design

This was a randomized, parallel-group phase 2 study with no masking. The registry lists 16 participants as enrolled. Nine are listed in the GSK2202083A group and seven in the Infanrix + Menjugate group. The two groups were assigned different vaccine courses, so the intended comparison was between the GSK2202083A schedule and the combination of Infanrix hexa and Menjugate.

The planned GSK2202083A course comprised doses at 3, 5 and 11 months of age. The comparator course comprised Infanrix hexa at those same ages and Menjugate at 3 and 5 months. Both descriptions specify intramuscular injections in the anterolateral quadrant of the right thigh. These are planned schedules in the arm descriptions; the registry record does not establish that each participant received every planned dose.

The study status is terminated. Its listed primary completion date is 2009-06-25, and its listed start date is 2009-04-01. The registry record does not report the reason for termination, the timing of the decision, or whether the termination followed a safety concern, an operational issue, or another circumstance. Those explanations should not be inferred from the status alone.

The study’s stated purpose was to evaluate safety and immunogenicity. Its primary measure concerned anti-PRP antibody concentrations at Month 3, while the listed secondary measures concerned adverse symptoms and events. The registry record explicitly states that no blood samples were taken because the study was terminated and that no immunogenicity analyses were done. Consequently, the design is known, but the principal planned antibody comparison is unavailable. The record also does not report a detailed statistical analysis plan, a sample-size justification, or a masked assessment procedure.

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: During the screening the following steps occurred: check for inclusion/exclusion criteria, contraindications/precautions, medical history of the subjects and signing informed consent forms.

Overall Study

Reasons for not completing this period:

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 Anti-PRP Antibody Concentrations ≥ 0.15 mg/mL, measured over At Month 3.

The primary endpoint was the number of subjects with anti-PRP antibody concentrations of at least 0.15 mg/mL at Month 3. Anti-PRP refers to antibody against the polyribosylribitol phosphate component associated with Haemophilus influenzae type b. A threshold-based endpoint classifies participants according to whether their measured antibody concentration reaches the specified level. It can describe the proportion of a study group meeting a prespecified immunologic criterion, rather than summarizing the full distribution of antibody concentrations.

In general, antibody thresholds are used to express whether measured immune responses meet a defined benchmark. The benchmark gives an interpretable classification, but it does not by itself describe how far concentrations lie above or below the threshold, how variable they are, or how responses change over time. Those questions require suitable measurements and analyses.

For this trial, the endpoint has no observed result. The registry record says the study was terminated, no blood samples were taken, and no immunogenicity analyses were done. Thus, the posted record does not establish how many participants met the threshold, the antibody concentrations in either group, or a difference between groups. The use of a clear threshold in the endpoint definition cannot compensate for the absence of measurements.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study is described as randomized, parallel-group, and unmasked. These design terms describe how the comparison was organized; they do not supply a result when outcome measurements are missing. The registry record lists 16 enrolled participants across the two groups. It does not report detailed procedures for random sequence generation, allocation concealment, or the statistical analysis plan.

What does randomization contribute?

In general, randomization assigns participants to study groups using a chance-based process. When properly implemented, it can reduce systematic differences between groups at assignment. It does not guarantee that the groups will be identical, particularly in a small study, and it cannot prevent bias arising after assignment, such as missing measurements or differences in follow-up. The registry identifies this trial as randomized but does not report the specific randomization procedure or concealment details.

The parallel model means participants were assigned to a group that followed its own planned vaccine course, rather than each participant receiving both courses in sequence. The record describes no masking. In general, masking can limit the influence of knowledge about assigned treatment on reporting, assessment, or other study conduct. Because this trial was unmasked, outcomes involving reported symptoms may be more open to expectation or reporting effects; the registry record does not describe additional safeguards or independent assessment.

Why is there no primary endpoint estimate?

The primary endpoint requires antibody measurements at Month 3. A threshold outcome would ordinarily be calculated by classifying each measured participant according to whether the antibody concentration reached at least 0.15 mg/mL, then reporting group-level counts or proportions and possibly a between-group comparison. In this study, the registry says no blood samples were taken and no immunogenicity analyses were done. Without measurements, neither a threshold count nor an antibody concentration summary can be estimated from the posted results. No recalculated immunogenicity result is available.

In general, an estimate is more informative when paired with a confidence interval. A confidence interval describes the range of effect estimates compatible with the observed data under the statistical method used. It conveys precision as well as direction and magnitude. Here, there is no primary endpoint estimate from which to construct such an interval. The registry record does not report a confidence interval, a p-value, or another inferential result for immunogenicity.

How should the safety counts be understood?

The registry lists group counts for serious adverse events and for other adverse events. The serious-event counts are 0 among 9 at risk in the GSK2202083A group and 0 among 7 at risk in the Infanrix + Menjugate group. The other-event counts are 5 among 9 and 5 among 7, respectively. These are descriptive participant counts. They are not estimates of the comparative risk adjusted for other factors, and the record does not provide confidence intervals or tests for them.

In general, adverse-event counts should be interpreted with attention to the event definition, observation period, denominator, severity, and assessment method. A count of participants with an event is different from a count of event episodes, because one participant may experience more than one event. The listed secondary outcomes distinguish solicited local symptoms, solicited general symptoms, unsolicited adverse events, and serious adverse events, but the record does not provide a complete breakdown of all these categories in the registry record reported. The broad other-event count should not be treated as a detailed account of specific symptoms.

Over-dispersion is a general statistical issue that can arise when count outcomes vary more than a simple model assumes. In that situation, standard errors from an overly restrictive model may understate uncertainty. It is not possible to assess over-dispersion from the aggregate counts alone, and the registry record does not report a count model or a dispersion assessment. No model-based comparison should be inferred from the descriptive figures.

What do the planning assumptions mean?

The registry record does not report a sample-size justification for the trial. The stated planning-illustration assumptions refer to a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a fraction of the observed effect. Such assumptions describe a calculation framework, not the actual design rationale or an observed result. The record does not provide a numerical effect-based planning estimate in the information available for this analysis. Because the primary outcome was not measured, an observed immunogenicity effect is unavailable for such an illustration.

In general, a sample-size calculation asks how many participants would be needed for a specified design to detect an assumed effect with a chosen level of statistical power. That calculation depends on the outcome, variability or event rate, effect size, significance level, allocation, and analysis method. It is a planning exercise, not evidence that a study had a particular probability of success after completion. A calculation based on an observed effect is especially dependent on that estimate and should not be mistaken for observed power. No sample-size illustration can replace missing primary endpoint data in this trial.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including the primary anti-PRP antibody measure and secondary safety outcomes. The secondary outcomes concern participants with solicited local symptoms, solicited general symptoms, unsolicited adverse events, and serious adverse events. Examining several outcomes can raise a multiplicity issue: in general, the more statistical tests performed, the greater the chance of at least one result appearing unusual by chance if each test is interpreted separately. The registry record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or a prespecified testing strategy.

The primary endpoint cannot be analyzed because no blood samples were taken. The record states that no immunogenicity analyses were done, and it lists no analyses. The available adverse-event counts are descriptive; the registry record does not report inferential tests for them. There is consequently no reported family of p-values or confidence intervals from which to assess multiplicity adjustments.

Missing data are central to interpretation, but the available record does not describe participant-level completion, withdrawal, or the handling of missing observations for each outcome. It explicitly identifies the absence of blood samples and the resulting absence of immunogenicity analyses. The reason for termination is not reported in the registry record. The record also does not define an intention-to-treat, per-protocol, or safety analysis population. The counts at risk are stated for the adverse-event groups, but the analysis-population rules are not described. These gaps prevent assessment of whether outcome availability differed by group or whether any planned analysis population was followed.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse-event figures are 0 affected participants among 9 at risk in the GSK2202083A group and 0 among 7 at risk in the Infanrix + Menjugate group. The death count is 0 in each group. These are observed counts in the registry record; they do not demonstrate that the possibility of a serious event or death is absent.

The other adverse-event field lists 5 affected participants among 9 at risk in the GSK2202083A group and 5 among 7 at risk in the Infanrix + Menjugate group. These figures should be read as participant counts, not as a count of all event episodes. The record does not provide detailed event descriptions, timing, severity, or causal attribution for these counts. Its listed secondary outcomes include solicited local and general symptoms, unsolicited adverse events, and serious adverse events, but the figures alone do not provide a complete clinical description of those categories.

In general, safety counts are descriptive evidence collected under the study’s observation and reporting procedures. The registry record does not report confidence intervals or a formal comparison for these figures. The small enrolled groups and absence of detailed event information limit how precisely they characterize safety.

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

The record documents a randomized phase 2 feasibility study intended to evaluate safety and immunogenicity in healthy infants. It describes two planned vaccine courses and identifies a Month 3 anti-PRP antibody threshold as the primary endpoint. It also reports limited adverse-event counts. These registry entries describe the study’s plan and the available safety information; they do not establish the primary immunogenicity result.

The endpoint was not measured: no blood samples were taken, and no immunogenicity analyses were done. The posted results therefore do not show how many participants reached the antibody threshold, what antibody concentrations were observed, or whether the groups differed. The absence of a result is not evidence that the groups had the same response, nor does it show that one course had a higher response.

The adverse-event counts provide a narrow descriptive record. No serious adverse events and no deaths are listed in either group. Other adverse events are listed for 5 participants in each group, with the group-specific at-risk counts reported as 9 and 7. These figures do not identify the events or establish their relationship to vaccination. They also do not provide a precise comparative estimate with stated uncertainty.

The study status is terminated, but the reason is not reported in the registry record. It is therefore not possible to attribute the missing immunogenicity results to a particular operational, scientific, or safety cause. The record also does not report a detailed analysis plan or sample-size justification. These omissions limit interpretation of the intended inferential approach.

In general, a trial can contribute information about feasibility and study conduct even when its main endpoint is unavailable, but the specific conclusions depend on the data actually reported. For this record, the strongest supported conclusion is that the planned antibody analysis was not performed and that the listed safety counts are descriptive. No treatment-effect claim or comparative immunogenicity conclusion follows from the posted information.

13. Why This Trial Matters Statistically

This trial illustrates why a clearly defined endpoint and a completed measurement plan are both necessary for statistical interpretation. The primary endpoint specified an antibody threshold and a time point, but the registry record says that no blood samples were taken. Without measurements, the endpoint cannot be summarized, compared between groups, or accompanied by an estimate of uncertainty. A precise endpoint definition does not itself produce evidence.

The study also shows the difference between planned and observed information. The arm descriptions give detailed schedules for the two vaccine courses, while the record’s adverse-event fields provide some observed counts. Those details do not establish that every planned dose was received or supply the missing antibody results. Keeping intended procedures separate from measured outcomes is important when reading a terminated trial.

Randomized allocation can support a fair comparison when outcome data are collected and analyzed appropriately. It cannot resolve a comparison when the primary outcome is absent. Similarly, a zero count of serious adverse events is a useful description of what was recorded, but it does not establish that serious events are impossible. The small groups and lack of uncertainty estimates matter when considering how much can be learned from those counts.

For clinical researchers and statisticians, the record highlights the importance of transparent reporting of termination reasons, analysis populations, outcome completion, and statistical methods. These details help readers distinguish a null finding from an unavailable finding. Here, the antibody outcome is unavailable, not a reported null comparison. The registry record does not state why the study ended or provide a detailed analysis plan, so those questions remain unresolved.

The trial therefore matters as an example of how study status and data completeness shape the conclusions that can be drawn. Its documentation supports a description of the intended comparison and limited safety counts, but not an estimate of the primary immunogenicity outcome.

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 most important limitation is the absence of primary endpoint measurements. The registry record states that termination occurred before any blood samples were taken and that no immunogenicity analyses were done. As a result, the planned anti-PRP threshold outcome has no reported estimate, and no comparison between the vaccine groups is possible from the posted results.

The reason for termination is not reported in the registry record. The record also does not report whether all participants received their planned doses, the timing and completeness of safety follow-up, or how participants were included in each analysis. The group counts at risk are available for adverse events, but the analysis-population definitions are not described.

The study was unmasked, and the registry record does not describe procedures to reduce possible reporting or assessment effects. The record does not provide allocation concealment details, a full statistical analysis plan, a sample-size justification, confidence intervals, or formal tests. It also does not give detailed descriptions or causal assessments for the other adverse-event counts. The small enrolled groups further limit the amount of descriptive safety information available, especially for uncommon events.

These limitations do not establish why the study was terminated or imply a particular result. They define the boundaries of what the registry record supports: the planned design and endpoint are documented, the primary antibody data are unavailable, and the reported safety counts remain descriptive.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Feasibility Study of GlaxoSmithKline Biologicals' GSK2202083A Vaccine in Healthy Infants at 3, 5 and 11 Months of Age. — NCT00871741.
• Registry record last updated 2018-06-06; status last verified 2017-04.
• Results first posted 2017-04-04.
• 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

NCT00871741 is a randomized, open-label, parallel-group phase 2 study sponsored by GlaxoSmithKline. It enrolled 16 healthy infants and compared a planned three-dose course of GSK2202083A at 3, 5 and 11 months of age with planned Infanrix hexa doses at those ages plus Menjugate doses at 3 and 5 months.

The primary endpoint concerned anti-PRP antibody concentrations of at least 0.15 mg/mL at Month 3. The registry record states that the study was terminated, no blood samples were taken, and no immunogenicity analyses were done. It lists 0 serious adverse events and 0 deaths in each group, with other adverse events listed for 5 participants in each group. The reason for termination and a detailed statistical analysis plan are not reported in the registry record.