A Study to Evaluate Pneumococcal Polysaccharide Vaccine Effectiveness in Children With Type 1 Diabetes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Evaluate Pneumococcal Polysaccharide Vaccine Effectiveness in Children With Type 1 Diabetes (NCT04481243), a na phase 4 study. The primary outcome is Immunoglobulin G (IgG) Antibodies.

2. Clinical Question

3. Trial Design

This is a completed Phase 4, single-group study sponsored by Mayo Clinic. The registry record lists an enrollment of 29 and identifies children with type 1 diabetes as the study population. It records the study start as 2021-04-30 and primary completion as 2023-01-20. The study status is completed. The listed intervention is Pneumovax 23, described as pneumococcal polysaccharide vaccine, and the listed procedure includes a blood draw.

The design is not a randomized comparison. Allocation is recorded as not applicable, the model is single group, and masking is none. The arm description says that subjects with type 1 diabetes receive PPSV23. There is no like-for-like control arm in the record. This design can describe antibody measurements among participants following vaccination, but by itself it cannot separate vaccination-related changes from changes that might have occurred over time or from other influences.

The primary outcome is IgG antibodies measured in mcg/mL at 6 months post vaccination, with the parameter specified as a median and dispersion as an inter-quartile range. The record says three subjects withdrew before the 6 months post vaccination blood draw and one subject withdrew before receiving the vaccine. It does not report the final number contributing to the primary outcome, whether withdrawal categories overlap, or the analysis population used.

The record lists one outcome measure and no analyses. Specific eligibility criteria, recruitment procedures, vaccination schedule details beyond the stated intervention, and sample-size justification are not reported in the registry record. Nor does the record describe a protocol for assessing response adequacy or evaluating factors that may affect response. These omissions limit how fully the study's planned methods can be reconstructed.

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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Three subjects withdrew prior to the 6 months post vaccination blood draw and one subject withdrew prior to receiving the vaccine.

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 Immunoglobulin G (IgG) Antibodies, measured over 6 months post vaccination.

The primary endpoint is pneumococcal-specific immunoglobulin G (IgG) antibody concentration, measured in mcg/mL at 6 months post vaccination. Antibodies are proteins involved in immune recognition; measuring a vaccine-related antibody response provides a laboratory indicator of the immune response under study. The record describes a blood draw for assessment of pneumococcal-specific IgG titer.

The planned summary is the median, accompanied by the inter-quartile range. The median describes the central value after measurements are ordered, while the inter-quartile range describes the spread of the middle portion of those observations. These summaries can be useful when antibody measurements are asymmetric or contain unusually high or low values, because the median is less affected by extreme observations than the arithmetic mean. This is a general statistical property, not a statement about the distribution of the study's unreported measurements.

The endpoint is a laboratory measure, not a direct count of infections or other clinical outcomes. Although the study title and purpose refer to seroconversion and an adequate response, the registry record does not report a threshold or rule that defines either term. It also does not report the numerical median or inter-quartile range. Thus, the endpoint's measurement and timing are specified, but the posted results do not establish how large the observed response was or how it was classified.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical method specified for the primary outcome is a median with an inter-quartile range. This is a descriptive summary: it characterizes the observed measurements rather than estimating a treatment difference. The median is the middle observation when measurements are ordered. The inter-quartile range describes the interval spanning the middle half of the observations. In general, these summaries are often chosen for data that may be skewed, because a few extreme values have less influence on the median than on the mean. The registry record does not provide the antibody measurements, so the distribution and the actual summaries cannot be evaluated.

What does a single-group design estimate?

In a single-group study, the central descriptive target is the outcome among participants in that group who have measurements. Here, the group is described as children with type 1 diabetes who receive PPSV23, and the planned outcome is IgG at 6 months post vaccination. Such a summary can report the observed antibody levels at that time. It does not, on its own, estimate what would have happened to the same participants without vaccination. A separate comparator or another design-based source of comparison would be needed to estimate that contrast.

Allocation is recorded as not applicable, masking is none, and the study model is single group. These features mean that randomized allocation and blinded assessment are not described in the registry. In general, randomization can help balance measured and unmeasured factors between comparison groups, while masking can reduce some forms of knowledge-related influence on care or measurement. Those protections are not represented as design features. The endpoint is a laboratory measurement, but the record does not describe the laboratory procedures or whether assessment was blinded.

How should uncertainty be understood?

A confidence interval is a statistical range intended to express uncertainty around an estimated quantity under a specified method and assumptions. It is not a guarantee that the true value falls within a particular interval. For a median, uncertainty could be reported using an appropriate interval method; for a group contrast, an interval would address uncertainty in the contrast. No confidence interval or other uncertainty estimate is reported in the registry record. Since the actual IgG summary is also absent, neither the estimated level nor its precision can be described.

A p-value, when reported, measures how incompatible data are with a specified null hypothesis under the assumptions of a statistical test. It does not measure the probability that the null hypothesis is true, and it does not describe the size or clinical importance of an effect. The registry record lists no analyses and no p-values. There is therefore no reported hypothesis test to interpret. The absence of a posted test should not be read as evidence of either a statistically significant or a non-significant result.

Why do distribution and measurement choices matter?

Antibody concentrations can, in general, have a distribution in which many observations cluster while some are substantially higher or lower. For such data, the median and inter-quartile range may communicate the center and spread more transparently than a mean and standard deviation. This is general statistical guidance, not a claim about the distribution in this study. A plot or the underlying measurements could help assess shape, clustering, and unusual observations, but those data are not reported in the registry record.

The outcome is described in concentration units of mcg/mL. A concentration is a quantitative measurement, but an amount in those units is not automatically a clinical classification. To call a response adequate or to identify seroconversion, a decision rule or threshold must be specified and applied. No such threshold or classification rule is reported in the registry record. Consequently, the planned continuous antibody summary and the stated adequacy question are related but not interchangeable.

What can the listed analyses support?

The record lists one outcome measure and zero analyses. It does not report a model, a comparison, an adjustment strategy, or an analysis of factors affecting antibody response. The stated aim includes assessing such factors, but the registry record does not provide covariates, model assumptions, or results. No adjusted and unadjusted estimates can be contrasted, and no conclusions about predictors can be drawn from the posted information.

Sample-size calculations depend on a target effect, variability assumptions, a significance level, power, allocation, and the planned analysis. Those calculations are planning tools, not observations and not evidence that a study had a particular probability of detecting its observed result. A sample-size justification for this trial is not reported in the registry record. No actual power calculation or sample-size rationale should therefore be inferred from the enrollment count.

In general, over-dispersion occurs when observed variability exceeds what a chosen statistical model assumes. If ignored, it can make uncertainty appear smaller than it should be, depending on the model. The registry record does not report a model or evidence of over-dispersion for this study, so this is a general methodological consideration rather than a finding about these data.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and no analyses. It does not report a statistical analysis plan, prespecified hypothesis tests, or any adjustment for multiple comparisons. The study purpose mentions both assessing immune response and examining factors that may affect it, but the record does not specify how many factors were to be evaluated or how those evaluations were to be handled. It is therefore not possible to determine whether multiplicity was a practical issue in the analyses or whether a correction was planned.

Multiplicity is a general concern when many outcomes, subgroups, time points, or statistical tests are examined. As the number of tests grows, the chance of at least one apparently notable result can increase, even when no underlying association exists. Statistical methods can address that concern, but the appropriate approach depends on the questions and analysis plan. No such plan or adjustment is reported in the registry record. The absence of reported analyses also prevents assessment of whether the posted outcome represents all intended analyses.

The registry notes three subjects withdrew before the 6 months post vaccination blood draw and one withdrew before receiving the vaccine. It does not report reasons for withdrawal, the number with a measured primary endpoint, or the method used to handle missing outcomes. It is not stated whether participants with missing measurements were excluded, whether any values were imputed, or whether sensitivity analyses were conducted. Those procedures are not reported in the registry record.

The analysis population is also not defined. The record does not say whether the primary endpoint was analyzed among all enrolled participants, only those who received vaccine and completed follow-up, or another group. The counts of withdrawals alone do not establish the number included in an endpoint analysis. Without these details and the outcome values, the potential impact of missingness on the antibody summary cannot be assessed.

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 0% reporting threshold.

For the Pneumovax 23 group, the registry record lists 29 participants at risk for serious adverse events and zero serious adverse events. It also lists 29 participants at risk for other adverse events and zero other adverse events. Deaths are listed as zero. No top serious event terms are listed. These figures are the safety counts recorded in the registry; they are not a comparison against a control group.

A zero count means that no events are recorded in that category in the posted results. It should not be interpreted as proof that the underlying risk is zero, nor as evidence that an event could not occur. The registry record does not provide further detail about event definitions, the observation period for safety collection, severity grading, relatedness assessment, or completeness of reporting. Without those details, the scope of the counts cannot be fully evaluated.

Because this is a single-group study, the listed counts cannot establish whether event occurrence differed from what would have been observed under another treatment or without vaccination. They describe recorded events in the study group only. They also do not convey the primary IgG outcome, which is not numerically reported in the registry record.

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

The record documents a completed study of PPSV23 in children with type 1 diabetes, with a planned antibody measurement at 6 months post vaccination. It provides the endpoint definition, the single-group design, enrollment, withdrawal information, and selected safety counts. These details are useful for understanding what was intended to be measured and the context in which the study was conducted.

The most important limit is that the primary antibody results are not reported in the registry record. There is no median or inter-quartile range to describe, no confidence interval to indicate precision, and no stated rule for classifying a response as adequate or as seroconversion. The stated research question therefore cannot be answered from the posted results. The registry also lists no analyses, so there are no reported inferential results or findings about factors affecting response.

Even if an antibody summary were available, the design described would support a within-group description rather than a randomized comparison. With no control arm, differences attributable to vaccination cannot be isolated from time-related changes or other influences by a direct treatment contrast. The result would also apply to the measured study participants and would not automatically establish how outcomes would compare in a broader population.

The safety counts report zero serious events, zero other events, and zero deaths among the listed participants at risk. These are descriptive registry entries, not proof of no risk. The withdrawals before the planned blood draw also make the missing-outcome handling relevant, but that handling is not reported.

Accordingly, the record supports conclusions about the study's structure and reporting, but not a conclusion that the immune response was adequate or inadequate, or that the vaccine was effective or ineffective. Those judgments would require reported outcome data, a defined response criterion, and analysis details appropriate to the question.

13. Why This Trial Matters Statistically

This study is statistically informative as an example of the difference between a research objective and an interpretable result. The objective is to assess immune response and factors affecting it, while the listed primary measure is a quantitative IgG concentration at a specified follow-up time. A clear endpoint measurement is an important starting point, but interpretation also depends on reported values, uncertainty, analysis population, and any rule that turns the measurement into a category such as adequate response.

The single-group design is another important statistical feature. It can describe antibody measurements in participants who contribute data, but it does not provide a direct comparison group. This distinction helps prevent overinterpretation: an observed post-vaccination level is not itself an estimate of the difference between vaccination and an alternative. The registry's allocation and masking fields make the design limitations visible, while the absent endpoint results prevent even the descriptive response from being quantified.

The withdrawal information illustrates why outcome availability matters. The record notes withdrawals before vaccination and before the planned follow-up draw, but does not identify the number included in the endpoint analysis or the missing-data approach. Statistical summaries can depend on which participants have observed measurements. Without that accounting, readers cannot judge whether the reported analysis, if any, represents the enrolled group or a subset.

Finally, reporting of zero adverse events should be read as a recorded count, not as proof that risks are absent. The registry contains useful design and safety information, yet the absence of numerical primary results and analysis details sharply limits statistical interpretation. Recognizing both what is documented and what remains unreported is essential to a careful reading.

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 outcome is specified as IgG antibodies in mcg/mL at 6 months post vaccination, but its numerical median and inter-quartile range are not reported in the registry record. The title and purpose refer to seroconversion and an adequate response, but a threshold or operational definition for either is not reported. This prevents assessment of the measured response and how it relates to the stated objective.

The single-group design has no randomized comparator. Allocation is listed as not applicable, and masking is none. Thus, the record does not describe a direct comparison with an untreated group or an alternative intervention. Any descriptive result would not by itself establish a causal effect attributable to vaccination.

The record notes three withdrawals before the 6 months post vaccination blood draw and one before vaccine receipt. It does not report the reasons for these withdrawals, the endpoint analysis denominator, the analysis population, or how missing observations were handled. The potential influence of missing outcome data cannot be assessed from the registry information.

One outcome measure is listed, but no analyses are listed. The registry record does not report confidence intervals, tests, models, results for factors affecting response, or a statistical analysis plan. It also does not report a sample-size justification. Details such as eligibility criteria, laboratory methods, and event-monitoring procedures are not reported in the registry record, limiting assessment of measurement and study conduct.

The safety results list zero serious events, zero other events, and zero deaths among 29 participants at risk, but further event definitions and collection details are not reported. These counts should be understood within that reporting context and not as evidence that risk is absent.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study to Evaluate Pneumococcal Polysaccharide Vaccine Effectiveness in Children With Type 1 Diabetes — NCT04481243.
• Registry record last updated 2023-11-08; status last verified 2023-10.
• Results first posted 2023-11-08.
• 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

The registry record identifies a completed Phase 4, single-group study sponsored by Mayo Clinic, with 29 participants enrolled. The study population is children with type 1 diabetes, and the intervention is Pneumovax 23 (PPSV23). The record gives a start date of 2021-04-30 and primary completion date of 2023-01-20.

The primary outcome is pneumococcal-specific IgG antibodies in mcg/mL at 6 months post vaccination, summarized as a median with an inter-quartile range. Three subjects withdrew before the follow-up blood draw, and one withdrew before receiving vaccine. The registry lists one outcome measure and no analyses.

The numerical primary outcome, response threshold, analysis population, and missing-data method are not reported in the registry record. Safety entries list zero serious adverse events, zero other adverse events, and zero deaths among 29 participants at risk. The design does not include a randomized comparator, so the available record does not provide a direct treatment comparison.