B-cell Immunity to Influenza (SLVP017)- Year 5, 2013: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for B-cell Immunity to Influenza (SLVP017)- Year 5, 2013 (NCT03020537), a non-randomized phase 4 study. The primary outcome is Number of Participants Who Received Influenza Vaccine.

2. Clinical Question

3. Trial Design

This is a completed, phase 4, non-randomized study with a parallel model and no masking. Stanford University is the sponsor. The registry lists enrollment of 8 and gives a start date of 2013-10 and a primary completion date of 2013-12. Influenza is the listed condition.

The two described groups are children aged 1-2 years and adults aged 18-30 years. Children are characterized as seasonal influenza vaccine-naive and are described as receiving intramuscular, inactivated, trivalent influenza vaccine, Fluzone, in a pediatric formulation. Adults are described as not having received the 2012-2013 seasonal influenza vaccine and as receiving the same named vaccine type. The listed intervention is Fluzone.

The brief summary describes an exploratory interest in immune-response differences between age groups and between two vaccines given to identical twins and vaccine-naive young adults. However, the arm descriptions identify two age-based groups and one intervention. They do not explain the twin structure, identify a second vaccine, or describe a direct randomized comparison. Those details are not reported in the registry record.

Because allocation was non-randomized, differences between the groups cannot be interpreted as if the participants had been assigned to otherwise comparable treatment arms. Age and prior vaccination status distinguish the described groups, and the record does not specify an adjustment strategy to address such differences. The trial’s protocol, recruitment procedures, sample-size justification, and detailed statistical plan are not reported in the registry record.

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

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 Number of Participants Who Received Influenza Vaccine, measured over Day 0 to 28.

The primary endpoint is titled “Number of Participants Who Received Influenza Vaccine,” with participants as the unit and a timeframe of Day 0 to 28. It is a count endpoint: it describes how many participants met the stated event definition during the specified period. The record does not provide further operational detail about how receipt was verified or how the count was handled for participants with incomplete follow-up.

A count of participants with an event can describe whether the study’s stated activity took place in the enrolled groups. In general, event counts are easier to interpret when the event definition, observation period, and analysis population are clear. They can also be accompanied by a denominator and uncertainty estimate to show how much information the count carries. Those details help distinguish the observed count from an estimate meant to apply beyond the participants studied.

The registry names this as the primary endpoint, but its result is not reported in the registry record. No group-specific primary counts, denominators for this endpoint, effect estimate, confidence interval, or hypothesis test are listed. The exploratory summary’s interest in immune responses should not be mistaken for a reported primary immune-response outcome: the named primary endpoint is vaccine receipt, and immune-response endpoint results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a count endpoint describe?

A count endpoint records how many participants meet an event definition during a specified observation period. Here, the named primary endpoint counts participants who received influenza vaccine from Day 0 to 28. It is not a measurement of the strength or quality of an immune response. To interpret a count fully, readers generally need to know the event definition, the number of participants assessed, the analysis population, and how incomplete observations were handled. The endpoint title and timeframe are listed, but the primary result and these additional analysis details are not reported in the registry record.

How should group comparisons be understood?

In a randomized comparison, assignment is intended to make groups comparable on average, so differences in outcomes can be interpreted in light of the assigned interventions, subject to the study’s conduct and analysis. This is a general principle, not a description of this study’s allocation process. The record specifies non-randomized allocation. Its listed groups are children aged 1-2 years and adults aged 18-30 years, with different descriptions of prior seasonal-vaccination status. Consequently, an observed contrast between them would combine any vaccine-related difference with differences associated with age, prior vaccination, and potentially other factors. The registry does not report a statistical adjustment plan or analysis that accounts for these differences.

The parallel model indicates that the record describes distinct groups rather than a crossover sequence. The record does not provide enough detail to determine whether participants were individually linked as twins for an analysis, despite the brief summary’s reference to identical twins. Twin matching or paired analysis should not be assumed. The allocation method, masking status, and model are listed as non-randomized, none, and parallel, respectively; further procedural detail is not reported in the registry record.

What do uncertainty estimates add?

In general, an estimate calculated from a study sample is subject to sampling variability: a different sample could produce a different estimate. A confidence interval expresses uncertainty around an estimate under a specified statistical model. It is not a guarantee that a true value lies within a particular interval, and it does not address bias from a non-randomized design or incomplete measurement. No confidence intervals are reported for the listed endpoints, so the precision of estimates cannot be judged from the registry record.

A hypothesis test, when used, evaluates data against a stated null hypothesis under specified assumptions. A p value is not the probability that the null hypothesis is true, nor does it quantify the size or clinical importance of an effect. The record lists zero analyses and does not report p values, test statistics, or a prespecified hypothesis-testing plan. It would be inappropriate to infer a test from the endpoint descriptions alone.

Why can small event counts be difficult to interpret?

For a binary event, each participant is classified according to whether the event occurred under the study’s definition. General statistical methods for such data depend on the event count and the number of participants observed. When counts are sparse, estimates can be unstable, and a single participant’s outcome can have substantial influence on a group summary. The adverse-event entries in this record include small denominators, so descriptive counts should not be mistaken for precise comparative estimates. The registry does not report a model, interval estimate, or test for these safety data.

General methods for count data also rely on assumptions about how observations vary. In settings where variation exceeds what a simple model expects, over-dispersion can make standard errors too small and confidence intervals too narrow if it is ignored. This is a general consideration, not evidence that over-dispersion occurred in this study. The primary endpoint is a participant count, but the record does not report an analysis model or diagnostics from which to assess its assumptions.

What does the planning illustration mean?

The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Its stated effect to detect is a fraction of the observed effect. Such an illustration asks how a future study might be sized under those assumptions; it does not establish that the study was designed with that sample size, and it is not observed power. A planning calculation tied to an observed effect can also be highly uncertain, especially when the underlying estimate comes from a small exploratory study.

The illustration’s actual sample-size values and the particular effect fractions are not reported in the registry record. The trial’s own sample-size justification, any protocol-based target, and any assumptions used in its original design are also not reported in the registry record. The illustration therefore should be read only as a planning exercise under its stated assumptions, not as evidence that the enrolled study had adequate power for a particular scientific question.

Finally, the brief summary refers to immune-response differences, while the named primary endpoint is vaccine receipt. In general, a study’s stated scientific aim, registered endpoints, and analyzed outcomes may not be identical; interpretation should follow the endpoint definitions and results actually reported. Here, immune-response measures, their analysis methods, and their results are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Group A: 1 - 2 Years Old", "Group B: 18-30 Years Old")
n      <- c(1, 7)
events <- c(1, 7)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Group A: 1 - 2 Years Old  1  1  100.0  2.5  100.0  20.7  100.0  15.8  98.7
ARM  Group B: 18-30 Years Old  7  7  100.0  59.0  100.0  64.6  100.0  63.1  99.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary endpoint, “Number of Participants Who Received Influenza Vaccine,” and a secondary outcome concerning the number of participants with related adverse events. It also lists two outcome measures and zero analyses. The specific definitions of the outcome measures beyond the named endpoint and adverse-event outcome are not reported in the registry record.

Multiplicity arises when several outcomes, time points, subgroups, or statistical tests are evaluated. In general, the more comparisons made, the greater the chance of finding an apparently notable result by chance if no adjustment or prespecified hierarchy is used. The record does not report a multiplicity strategy, an outcome hierarchy beyond identifying the primary endpoint, or a statistical testing plan. No adjustment should be assumed.

The record does not describe missing-data rules, participant-level analysis populations, exclusions, or handling of incomplete follow-up. These details are important because missing outcomes can change the group included in an analysis and can affect interpretation, particularly in a small study. The primary endpoint’s timeframe is Day 0 to 28, but the registry does not report whether all enrolled participants contributed endpoint data across that period.

No protocol, statistical analysis plan, or analysis population definition is reported in the registry record. The absence of these details does not establish that no such documents or procedures existed; it means they are not available in this record. With no listed analyses or endpoint results, multiplicity handling and missing-data effects cannot be evaluated from the posted results.

12. 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 adverse-event entries separate a serious-event category from an “other” category. In Group A, the serious-event entry lists 0 affected among 1 at risk, and the other-event entry lists 1 affected among 1 at risk. In Group B, the serious-event entry lists 0 affected among 7 at risk, and the other-event entry lists 1 affected among 7 at risk. These are participant counts, not rates calculated from a larger population.

The record lists “Number of Participants With Related Adverse Events” as a secondary outcome. However, the provided group entries do not give event descriptions for the other category, and the serious-event terms list is empty. The record does not clarify the relationship assessment, event severity definitions, collection method, or observation period for these entries. Such details are not reported in the registry record.

The fields for deaths are null. A null entry means the death count is not reported in the registry record; it should not be interpreted as zero deaths. Sparse safety counts can describe what was recorded in the listed groups, but without fuller definitions and follow-up details they do not support broad comparative conclusions. No comparative safety analysis or uncertainty estimate is reported.

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

The record describes an exploratory, non-randomized study of influenza vaccination across two age-based groups, with total enrollment of 8. It identifies Fluzone and names vaccine receipt during Day 0 to 28 as the primary endpoint. It also records adverse-event counts. These registry entries characterize the study’s registry entry; they do not establish the magnitude or precision of a vaccine effect.

The posted results do not include the primary endpoint count, immune-response measurements, effect estimates, confidence intervals, or p values. Consequently, the record does not show how the primary endpoint differed between groups, whether immune responses differed, or how precisely any difference was estimated. The exploratory aim described in the brief summary should not be treated as a reported immune-response finding.

The groups were not randomized and differ in age, with prior seasonal-vaccination status described differently for each. A group contrast would therefore not isolate the effect of a vaccine. The record also does not fully explain the identical-twin reference or the two-vaccine comparison mentioned in the summary. Those limitations make it especially important not to read the group labels as a controlled treatment comparison.

In general, statistical significance and clinical importance are separate questions: a test result alone does not establish the size, relevance, or reliability of an effect. Here, no inferential results are reported, so neither statistical significance nor effect precision can be evaluated. The record can be read as documentation of a completed exploratory study and its listed outcomes, but it does not supply the outcome results needed to make a statistical claim about immune response or vaccine effects.

14. Why This Trial Matters Statistically

This record illustrates how a trial’s scientific motivation and its registered primary endpoint can differ. The brief summary describes exploratory interest in immune-response differences by age and vaccine, while the primary endpoint is the number of participants who received influenza vaccine during Day 0 to 28. Statistical interpretation depends on distinguishing the motivating question from the outcome actually named and reported.

It also highlights the importance of design when comparing groups. A non-randomized comparison between children and adults is not equivalent to a randomized comparison of otherwise similar participants. Age and prior seasonal-vaccination status distinguish the listed groups, and the registry does not report an adjustment analysis to address these differences. Statistical methods cannot, by themselves, remove design-related ambiguity when key factors are not measured or modeled.

The sparse safety counts show why denominators and event definitions matter. Counts can be informative descriptions of what was recorded, but they do not automatically provide precise estimates or a reliable between-group comparison. Reporting the analysis population, follow-up, event definitions, and uncertainty would help readers understand what the counts can support.

Finally, the absence of endpoint results and inferential analyses limits what can be learned from the registry entry. A completed status does not itself communicate the study’s findings. The record is a useful reminder that registration details, observed results, and statistical interpretation are distinct kinds of information, and that missing result details should not be filled in by assumption.

15. 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.

Several limitations are specific to the information recorded for this study. Enrollment was 8, and the described groups cover children aged 1-2 years and adults aged 18-30 years. With groups this small, even descriptive counts represent limited information, and estimates would generally be sensitive to individual outcomes. The registry does not provide precision estimates that would allow the uncertainty to be quantified.

The non-randomized design does not support treating the age groups as interchangeable control arms. They differ by age and in their stated prior seasonal-vaccination status. The record does not report a plan for adjustment, matching, or other methods to address these differences. It also does not clarify whether identical twins were included as linked participants or how the reference to two vaccines relates to the single listed intervention and the two arm descriptions.

The primary endpoint result and immune-response results are not reported in the registry record. The record lists zero analyses, so no statistical comparison, confidence interval, or test result is available to assess. The protocol, sample-size justification, detailed statistical plan, missing-data handling, analysis populations, and multiplicity strategy are not reported in the registry record.

For safety, event descriptions and details of ascertainment are not reported. The deaths fields are null, rather than reported counts. The adverse-event entries therefore support only a limited reading of the listed counts and do not establish comparative safety. The planning illustration is not the study’s own design justification, and its numeric outputs are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: B-cell Immunity to Influenza (SLVP017)- Year 5, 2013 — NCT03020537.
• Registry record last updated 2018-06-06; status last verified 2018-05.
• Results first posted 2017-03-09.
• 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.

19. Record Summary

NCT03020537 is a completed, phase 4, non-randomized, parallel study sponsored by Stanford University. The record lists enrollment of 8, no masking, and dates of 2013-10 to 2013-12. The described groups are children aged 1-2 years and adults aged 18-30 years; both are listed as receiving Fluzone, with a pediatric formulation specified for children.

The primary endpoint is the number of participants who received influenza vaccine during Day 0 to 28. A secondary outcome concerns participants with related adverse events. The registry includes sparse adverse-event counts but does not report the primary endpoint result, immune-response results, or statistical analyses. It also does not report a detailed analysis plan, sample-size justification, missing-data approach, or multiplicity strategy. The non-randomized, age-based groups are not like-for-like control arms.