This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Evaluating Immune Response to Seasonal FluMist in Healthy Adults (NCT01673425), a na na study. The primary outcome is IgA Antibody Titers.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01673425 |
| Phase | NA |
| Condition | Influenza |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 5 |
| Arms in the primary outcome | n/a |
| Lead sponsor | National Center for Occupational Health and Infection Control |
| Results posted | Yes |
2. Clinical Question
Population
Healthy adults, as described in the study title. The registry record lists five participants enrolled. Further eligibility details, including age limits or other health criteria, are not reported in the registry record.
Intervention
Live Attenuated Influenza Vaccine (LAIV), also known as FluMist. The record describes a single-intervention study in which participants were to receive LAIV rather than injectable flu vaccine. The record does not establish how many enrolled participants received the intervention.
Comparator
No concurrent comparator group is listed. The study is identified as single-group, with allocation recorded as NA and masking as none. Injectable flu vaccine is mentioned as the alternative to LAIV, not as a study arm for a direct comparison.
Primary question
The primary endpoint was change from baseline in IgA antibody titer at six weeks. The study rationale proposed that anti-flu IgA in adults’ nasal secretions might neutralize the weakened vaccine virus and help explain why LAIV was described as less effective in adults than in children. The record reports no analysis testing that hypothesis.
In practical terms, the planned question concerned whether an antibody measure changed after vaccination in a group of adults. A single-group before-and-after assessment can describe change over time within participants, if measurements and an analysis are available. Without a concurrent comparison group, it cannot by itself separate a vaccine-associated change from other explanations, such as natural variation in the measurement. In this study, the registry states that analyses were not conducted because nasal wash samples were inconclusive. Therefore, the posted record does not answer whether IgA titers changed or whether any change was related to LAIV.
3. Trial Design
The registry record identifies NCT01673425 as an interventional study evaluating immune response to seasonal FluMist in healthy adults. Its model is single-group, allocation is recorded as NA, and masking is listed as none. The intervention is Live Attenuated Influenza Vaccine. The arm description says participants would receive LAIV instead of injectable flu vaccine; it does not list an injectable-vaccine arm. This is not a randomized head-to-head comparison.
The record lists five participants enrolled. The study began in 2012-09, had primary completion in 2012-12, and is marked terminated. The stated reason for termination was poor enrollment. The registry lists the phase as NA. Further information about the study setting, eligibility rules, recruitment, vaccine administration, follow-up visits, or the timing of sample collection is not reported in the registry record.
The primary outcome was IgA antibody titers, with a timeframe of change from baseline at six weeks. Serum antibody response to LAIV is listed as a secondary outcome. The record notes two outcome measures but lists zero analyses. It explicitly says analyses were not conducted because nasal wash samples were inconclusive. Consequently, the study design identifies what the investigators intended to assess, but the registry record does not include analyzed results for either outcome.
The record does not report a statistical analysis plan, a sample-size justification, or a planned analysis population. Any sample-size planning assumptions accompanying the results are illustrations rather than the trial’s own design. They should not be interpreted as evidence that the enrolled study had a particular power or that its enrollment target was justified by a documented protocol calculation.
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
| Stage | Experimental: Live Attenuated Influenza Vaccine |
|---|---|
| STARTED | 5 |
| COMPLETED | 4 |
| NOT COMPLETED | 1 |
Analysis population for the primary outcome, as defined in the registry: This study was terminated due to poor enrollment. Analyses were not conducted due to inconclusive nasal wash samples.
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.
| Characteristic | Unit | Live Attenuated Influenza Vaccine Study |
|---|---|---|
| Participants analysed | 5 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 5 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 4 |
| Sex: Female, Male: Male | Participants | 1 |
| Region of Enrollment: United States | participants | 5 |
6. Primary Endpoint
The registry lists the primary outcome as IgA Antibody Titers, measured over Change from baseline in antibody titer at 6 weeks.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is described as change from baseline in antibody titer at six weeks, with IgA antibody titers as the named outcome. An antibody titer is a measure of antibody response. In general, measuring change from a participant’s baseline can describe how an immune marker differs between the initial measurement and a later assessment. It is a within-participant measure, not a direct comparison with another treatment group.
The study rationale focuses on anti-flu IgA in nasal secretions and the possibility that these antibodies could neutralize the weakened vaccine virus. The record also says that nasal wash samples were inconclusive, which prevented analyses. It does not give a numerical IgA result, an estimate of change, or an explanation of how inconclusive samples were defined or handled. The endpoint’s unit, statistical parameter, and measure of dispersion are not reported in the registry record. The specific collection and laboratory procedures are also not reported in the registry record.
As a general matter, an antibody measure can address an immune-response question, but it is not interchangeable with a clinical outcome such as the occurrence of influenza. The registry record presents this endpoint as an immune-response measure and contains no analyzed findings that establish the size, direction, or precision of any change.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the registry record reports no outcome analyses. It states that the study was terminated due to poor enrollment and that analyses were not conducted because nasal wash samples were inconclusive. Thus, there is no posted estimate of change in IgA antibody titers at six weeks, no estimate for the secondary serum antibody response, and no inferential result to interpret.
The enrolled sample was five participants. That enrollment count describes the size of the study; it does not indicate how many had usable paired measurements, how many received LAIV, or how many were included in an analysis. Those details are not reported in the registry record. Because the record says analyses were not conducted, it is not possible to describe an observed immune-response effect from the posted results. It is also not appropriate to treat the absence of an estimate as a finding of no change.
There is no reported confidence interval, p-value, standard error, or other measure of statistical uncertainty for the primary endpoint. General interpretation: an estimate describes the observed magnitude and direction of a quantity, while a confidence interval describes the range of values compatible with the data and the method used. Neither can be interpreted when the corresponding analysis and estimate are absent. Likewise, a non-significant result cannot be inferred: no statistical test is reported.
The single-group structure also limits what the intended endpoint could establish, even if a before-and-after analysis had been completed. General interpretation: a within-group change can describe how a measure varies over time among participants, but it does not isolate the effect of an intervention from other possible causes of change. A concurrent comparison group can help address that distinction, depending on how the study is designed and analyzed. No such group is listed in this record.
The stated hypothesis about nasal IgA is a rationale, not a result. The study’s termination and inconclusive samples leave that hypothesis untested in the posted analyses. The record supports describing the intended question, the design, the enrollment, and why analyses were not performed. It does not support a conclusion about whether LAIV changed antibody titers, the degree of any change, or how reliably such a change could be estimated.
Any planning illustration based on an observed effect should be read separately from the trial findings. The registry’s planning assumptions characterize such calculations as illustrations, not the trial’s own design. They do not supply a missing outcome estimate or replace the absent analysis. No sample-size justification for this study is reported in the registry record.
9. Statistical Methods Explained
The record identifies a single-group study with no masking and no randomized allocation. It lists one intervention, LAIV, and no concurrent comparator. These features describe the structure of the study; they do not identify which statistical procedures were planned or used. The registry reports zero analyses and states that analyses were not conducted because nasal wash samples were inconclusive.
What does a single-group design allow?
General: in a before-and-after design, each participant may contribute a baseline measurement and a later measurement. An analysis can summarize the change within participants, rather than comparing separate groups. The primary outcome’s stated timeframe, change from baseline at six weeks, is consistent with a planned assessment of within-participant change. However, the record does not say which statistical method would have been used, and the analysis was not conducted. It therefore cannot be assumed that a particular paired test, model, or summary statistic was part of the plan.
General: a within-participant comparison can account for the fact that two measurements from one person are related. It does not, on its own, establish why a measurement changed. Without a concurrent comparator, changes over time may have explanations other than the intervention. This is a design limitation rather than a defect that can be corrected simply by choosing a different statistical test.
What do estimates and uncertainty measures convey?
General: an estimate gives a numerical summary of the quantity being studied, such as an average change or another defined measure of change. A confidence interval communicates uncertainty around an estimate under specified assumptions and a specified analysis. A standard error is another summary of estimation uncertainty. A p-value, when used, assesses compatibility between observed data and a specified null hypothesis under the test’s assumptions; it is not a measure of the size or importance of an effect.
None of these results is listed for the primary endpoint. The registry also does not provide a numerical outcome, unit, dispersion measure, or statistical parameter. Consequently, there is no estimate to assess for size or direction and no interval with which to assess precision. General statistical explanations of these measures cannot fill in the missing trial results.
Why do sample size and variability matter?
General: a small study often has limited ability to estimate a quantity precisely, especially when the outcome varies substantially between participants. The precision of an estimate depends on the number of usable observations, the variability of the outcome, and the analysis method. The enrollment count alone does not establish the number of usable observations for a particular endpoint. In this record, sample quality prevented analysis, and the number of participants with usable paired measurements is not reported in the registry record.
General: over-dispersion describes variability greater than a chosen statistical model would expect. When present, a model that understates variability can produce overly narrow uncertainty intervals or tests that appear more decisive than warranted. No outcome distribution or dispersion estimate is reported, so there is no basis to assess whether over-dispersion arose or whether a particular model would have needed adjustment. This is a general consideration, not a claim about this study’s data.
The registry’s sample-size assumptions describe planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect defined as a stated fraction of an observed effect. The assumptions also distinguish total events for time-to-event calculations from participants per arm for other calculations. These are generic planning conditions, not evidence that this single-group study used a two-arm design. The record does not report a sample-size justification for the trial, and no observed primary-outcome analysis is available to interpret as an effect estimate.
What analysis details are absent?
The statistical test or model, handling of repeated measurements, covariate adjustment, missing-data method, confidence-interval method, and any interim-analysis plan are not reported in the registry record. The analysis population is not reported in the registry record. The record does not state whether any prespecified analysis plan existed outside the registry. Since no analyses were conducted, there are no model assumptions or diagnostic checks to evaluate. These absences should be kept distinct from evidence that a particular method was used incorrectly: the registry simply does not document the methods or results needed for that assessment.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists two outcome measures: primary IgA antibody titers and secondary serum antibody response to LAIV. It reports zero analyses and says analyses were not conducted because nasal wash samples were inconclusive. Accordingly, the record does not give estimates or inferential results for either outcome.
Multiplicity concerns can arise when several outcomes, time points, subgroups, or statistical tests are examined. General: when many hypotheses are tested, the chance of at least one apparently noteworthy result can increase unless the analysis plan accounts for the number and structure of those tests. Whether and how to control that issue depends on the planned scientific questions and statistical methods. A multiplicity adjustment or hierarchy for outcomes is not reported in the registry record. With no analyses conducted, there are no posted tests whose multiplicity adjustment can be assessed.
The registry does not explain how inconclusive nasal wash samples affected individual participants’ measurements, whether any samples were usable for particular endpoints, or whether other forms of missing data occurred. A missing-data method, such as imputation or an analysis restricted to observed measurements, is not reported in the registry record. The reason for the inconclusive samples is not reported in the registry record. No missingness assumptions can therefore be evaluated from the posted information.
The analysis population is not reported in the registry record. The five enrolled participants should not automatically be treated as five participants with analyzable primary-outcome data, since the record says sample inconclusiveness prevented analyses. The number with complete baseline and six-week measurements, and any participant-level disposition information, are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Study Enrollment | 0 | 5 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Study Enrollment | 0 of 5 |
The registry lists five participants at risk in the study-enrollment group and zero serious adverse events. It also lists zero other adverse events for five participants at risk. These are the posted event counts; they are not an analysis of comparative safety because no control group is listed.
The death field is null, rather than a numerical count. A null entry should not be read as a reported count of zero deaths; deaths are not reported in the registry record. The record does not provide event descriptions, timing, severity details beyond the serious-event category, or an explanation of how safety events were collected. It also does not establish from these fields how many enrolled participants received LAIV or contributed follow-up information.
General: an observed count of zero events in a small group does not establish that the underlying event risk is zero. Event counts are descriptive, and their interpretation depends on the number of participants observed, the duration and completeness of follow-up, event ascertainment, and the definition used. Those details are not fully reported in the registry record. The posted figures should therefore be read as registry counts for this small study, not as proof that no safety events could occur.
12. What the Result Does, and Does Not, Mean
The record establishes that a single-group study of LAIV in healthy adults was registered, that five participants were enrolled, and that the study was terminated because of poor enrollment. Its planned primary endpoint was change from baseline in IgA antibody titer at six weeks. The record further states that analyses were not conducted because nasal wash samples were inconclusive. Those details describe a study that did not produce a posted analysis of its primary immune-response question.
The result does not show that IgA titers increased, decreased, or remained unchanged. No numerical outcome estimate or uncertainty measure is reported. The lack of an analysis is not equivalent to a finding of no effect, and it does not establish that the hypothesis in the study rationale was false or true. The record also does not show a comparison between LAIV and injectable flu vaccine: injectable vaccine is mentioned as an alternative, but no comparator arm is listed.
General: an immune marker can help characterize a biological response, but a change in a marker is not itself proof of a change in a clinical outcome. Here, the record reports no analyzed immune-marker change and no clinical comparison. It therefore cannot support a conclusion about the clinical effects of LAIV or a difference between treatments.
The safety fields list zero serious adverse events and zero other adverse events among five participants at risk, while deaths are not reported in the registry record. These limited counts are descriptive and do not establish the absence of risk. More broadly, the record’s missing endpoint analyses, small enrollment, inconclusive samples, and lack of a comparator leave the intended efficacy-related question unresolved.
13. Why This Trial Matters Statistically
This study illustrates an important distinction between a registered research question and an answer supported by analyzed data. The record specifies an immune-response endpoint and a follow-up timeframe, but it also documents that the study ended after poor enrollment and that inconclusive nasal wash samples prevented analysis. Registration of an endpoint does not ensure that a usable estimate will be available.
The example also shows why outcome quality and study conduct matter alongside the choice of statistical method. General: statistical analysis depends on measurements that are sufficiently interpretable for the question at hand. If samples do not support a reliable measurement, a sophisticated model cannot recover information that is not available. Here, the registry identifies sample inconclusiveness as the reason analyses were not conducted, while details about the cause or extent of that problem are not reported in the registry record.
The single-group design highlights a separate inferential boundary. A before-and-after endpoint can be useful for describing within-participant change, but a concurrent comparison is generally needed to distinguish intervention-associated change from other time-related influences. This study lists no comparator arm, and the registry contains no analysis in any event.
Finally, the record is a reminder to distinguish an inconclusive or unavailable result from a negative result. No estimate is not an estimate of zero. Reporting that no analysis was conducted helps readers avoid treating an unreported effect as evidence of no change, and helps keep the study’s stated biological hypothesis separate from findings the data did not establish.
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 principal limitation for interpreting outcomes is that the registry explicitly says analyses were not conducted. The nasal wash samples were inconclusive, and the study was terminated due to poor enrollment. The record does not report a primary-outcome estimate, a secondary-outcome estimate, or statistical uncertainty for either endpoint.
Enrollment was five, but the number of participants with usable samples or complete baseline and six-week measurements is not reported in the registry record. It is not stated how many participants received LAIV, how long each participant was followed, or whether participants discontinued or had missing visits. These omissions prevent assessment of endpoint-specific denominators and data completeness.
The study has no listed comparator group, with allocation recorded as NA and masking as none. It therefore cannot provide a randomized comparison with injectable flu vaccine. In addition, the record does not report detailed eligibility criteria, sample collection and laboratory methods, a statistical analysis plan, a sample-size justification, or methods for handling inconclusive or missing measurements.
The registry reports zero serious adverse events and zero other adverse events among five participants at risk, but deaths are not reported in the registry record. Detailed event definitions, ascertainment procedures, and follow-up completeness are not reported in the registry record. These safety counts should not be generalized beyond the limited information documented for this study.
Finally, the stated hypothesis about nasal IgA is not accompanied by an analyzed result. The record supports identifying that hypothesis as the study rationale, but not concluding whether it was supported. The short enrollment period listed in the record does not resolve these data and design limitations.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluating Immune Response to Seasonal FluMist in Healthy Adults — NCT01673425.
- Registry record last updated 2021-01-27; status last verified 2014-08.
- Results first posted 2014-09-04.
- 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.
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18. Record Summary
NCT01673425 was a single-group study evaluating Live Attenuated Influenza Vaccine in healthy adults. The registry lists five participants enrolled, no masking, and no comparator arm. The primary endpoint was change from baseline in IgA antibody titer at six weeks; serum antibody response to LAIV was a secondary outcome.
The study began in 2012-09, had primary completion in 2012-12, and is marked terminated due to poor enrollment. The registry states that analyses were not conducted because nasal wash samples were inconclusive. No analyzed outcome estimates or statistical uncertainty measures are posted. The safety record lists zero serious adverse events and zero other adverse events among five participants at risk; deaths are not reported in the registry record. The central statistical interpretation is therefore that the planned immune-response question remains unanswered in the posted results.