Safety Study to Assess IV Zanamivir for Treatment of Influenza Infection in Patients Who Are in Hospital: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety Study to Assess IV Zanamivir for Treatment of Influenza Infection in Patients Who Are in Hospital (NCT01014988), a na phase 2 study. The primary outcome is Number of Participants With Any Adverse Event (AE) Considered to be Related to Study Treatment.

2. Clinical Question

The clinical question is therefore a descriptive safety question in hospitalized participants with confirmed influenza. The record also names secondary outcomes concerning virologic improvement, viral load, susceptibility, treatment-emergent mutations, vital signs, ventilation and oxygen use, and return to pre-morbid functional status. Those topics broaden the study’s clinical scope, but they do not turn its single-arm design into a controlled test of treatment benefit.

In general, a single-arm safety study can describe events observed during and after treatment and can identify events that warrant further evaluation. Without a concurrent control group, however, it cannot establish how often those events would have occurred in similar patients under another treatment or without the study drug. The registry does not report a treatment-related primary-outcome count, so the primary clinical question cannot be answered from the posted primary result.

3. Trial Design

The registry identifies NCT01014988 as a phase 2, completed study sponsored by GlaxoSmithKline. It lists enrollment of 202 and describes an open-label, multi-center, single-arm study of intravenous zanamivir in hospitalized adults, adolescents, and children with confirmed influenza. The listed start is 2009-11, and primary completion is 2015-02.

Open-label means that the study was not masked. The intervention was zanamivir aqueous solution, and the registry lists no allocation to competing treatment arms. The single-arm design was described as serving the primary objective of providing safety data, including the possibility of providing safety data on a real-time basis if necessary. The record does not report additional operational details about that process.

Enrollment is not necessarily identical to the number included in a particular analysis. The primary outcome population is defined as participants who received >=1 dose of study medication. The registry lists safety counts in age cohorts, with the number at risk varying across cohorts. It does not report a single total for the primary outcome population or explain any differences between enrollment and the populations used for individual outcomes.

Because participants were not randomized between study treatments and there was no control arm, the design supports descriptive reporting rather than a like-for-like treatment comparison. Changes in symptoms, viral measures, or clinical support over time could be described within participants, but without a comparator those changes cannot isolate the effect of zanamivir from the course of influenza, other care, or other influences. The registry record does not report a protocol-level statistical plan, a sample-size justification, or a detailed analysis plan.

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: Male or female participants who were \>=6 months of age, hospitalized with laboratory-confirmed influenza, and able to receive study drug within 7 days of influenza symptom onset were enrolled in the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety Population: participants who received \>=1 dose of study medication.

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Any Adverse Event (AE) Considered to be Related to Study Treatment, measured over Up to post-treatment (PT) + 23 days.

The primary endpoint is the number of participants with any adverse event considered related to study treatment. An adverse event is defined broadly as an untoward medical occurrence temporally associated with use of a medicinal product, whether or not it is considered related. It can include an unfavorable or unintended sign, an abnormal laboratory finding, a symptom, or a new or worsened disease. Investigators assessed whether each event was related to study treatment.

The endpoint is evaluated in the safety population: participants who received >=1 dose of study medication. Its timeframe is up to post-treatment (PT) + 23 days. Counting participants rather than event episodes gives a direct description of how many people experienced at least one event meeting the endpoint definition; it does not indicate the number of separate events each participant experienced or their severity.

In general, this kind of endpoint is used in safety-focused studies because it records events occurring during a defined treatment and follow-up period. Investigator attribution is part of the endpoint, but temporal association alone does not establish that treatment caused an event. The registry record does not report a result for this primary endpoint, so its observed count and the precision of that count are not available in the posted primary outcome information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a single-group study and lists no analyses. It does not report the statistical methods used to analyze the primary or secondary outcomes. The explanations below are general descriptions of how such methods are commonly interpreted; they should not be taken as a claim that any particular method was used in this study.

What does a participant count describe?

A participant count records how many people meet an outcome definition. For an adverse-event endpoint, that requires defining the event, the population included, and the observation period. Here, the primary definition concerns any adverse event judged by the investigator to be related to treatment, among participants who received >=1 dose, through post-treatment (PT) + 23 days. The outcome is a count of participants, rather than a measure of the number of event episodes or the time until an event.

Counts are most informative when their denominator and eligibility rules are clear. The registry gives cohort-level numbers at risk for the adverse-event listings, while the primary outcome population is described in words. It does not report a primary-outcome count or a separate primary-outcome denominator. A reader should therefore not assume that enrollment, the safety population, and every outcome-specific population are identical.

Why does the design matter for inference?

In general, random assignment to concurrent groups can help make treatment groups comparable with respect to both measured and unmeasured factors. This study has no randomized comparison and no separate control arm. A single-arm count can describe events among treated participants, but it cannot estimate the difference between treatment strategies. Events may reflect the underlying infection, the circumstances of hospitalization, other care, participant characteristics, treatment, or combinations of these factors. The design alone cannot separate those explanations.

Open-label status means treatment was not masked. For an outcome that includes investigator judgment about relatedness, awareness of treatment can be relevant to assessment. That observation is a general methodological consideration, not evidence that assessments in this study were biased. The registry record does not describe additional safeguards or procedures for adjudicating relatedness.

How should uncertainty be understood?

In general, a confidence interval gives a range of values compatible with an estimate under a stated statistical model and procedure. A narrow interval indicates greater precision than a wide interval, while neither width nor location proves causation. For a single-arm safety count, an interval could describe uncertainty about the observed event frequency if an appropriate analysis and denominator were reported. No confidence interval or primary-outcome estimate is reported in the registry record. A p-value would address a specified statistical hypothesis under a model; without a comparison or a stated hypothesis, it would not by itself answer whether treatment caused an event. No p-value or testing procedure is reported.

For count outcomes, statistical methods may need to account for how counts vary across participants. In general, over-dispersion occurs when observed variation exceeds what a chosen model expects; ignoring it can make uncertainty estimates too optimistic. That issue is relevant to some event-count analyses, but the primary endpoint is defined as the number of participants with any qualifying event, and the registry does not report a model for it. No claim about over-dispersion or a particular count model can be made from the record.

What do the planning assumptions mean?

In general, sample-size calculations describe the number of participants or events that a hypothetical design would need to target a stated effect under specified assumptions. They are planning illustrations, not observed study results and not retrospective proof of power. The stated planning framework uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect defined as a fraction of an observed effect. It specifies total events for time-to-event illustrations using the Schoenfeld approach and participants per arm for other illustrations.

Those assumptions describe a hypothetical two-arm planning exercise, not this single-arm trial’s allocation. They do not establish that the trial was planned or analyzed that way. The registry record does not report the trial’s sample-size justification or a protocol-based power calculation. The record also does not provide the primary outcome result needed to assess a planning illustration based on an observed primary effect. Any displayed planning figures should consequently be understood as hypothetical planning quantities, not as evidence about the study’s observed precision or power.

The registry lists 34 outcome measures and zero analyses. This does not establish that no analyses were performed; it indicates that no analyses are listed in the registry information. The analysis population for each secondary outcome, handling of repeated measurements, model choices, and any adjustment for multiple testing are not reported in the registry record. Those omissions limit independent assessment of how estimates were obtained and how uncertainty should be interpreted.

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("Cohort 6: Adults (18 Years and Older)", "Cohorts 1-5: Pediatrics/Adolescents (6 Months to <")
n      <- c(130, 71)
events <- c(28, 5)
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  Cohort 6: Adults (18 Years and Older)  130  28  21.5  14.8  29.6  15.3  29.4  15.4  29.4
ARM  Cohorts 1-5: Pediatrics/Adolescents (6 Months to <  71  5  7.0  2.3  15.7  3.0  15.4  3.1  15.5

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 34 outcome measures, spanning safety, virologic outcomes, vital signs, ventilation and oxygen use, and functional status. It lists zero analyses. A list of outcomes does not show which outcomes were formally analyzed, which were designated primary or secondary in the protocol, or which results were selected for reporting. The statistical approach to multiplicity is not reported in the registry record.

In general, when many outcomes or repeated comparisons are examined, the chance of at least one apparently unusual result can increase. Multiplicity procedures may control that risk or distinguish confirmatory analyses from exploratory ones. No adjustment method, hierarchy of hypotheses, or other multiplicity strategy is reported. The absence of a listed strategy should not be interpreted as evidence that no strategy was used outside the registry record.

Missing-data methods are also not reported. The registry record does not describe how unavailable measurements, early discontinuation, or incomplete follow-up were handled for the primary or secondary outcomes. It does not report whether outcome-specific denominators changed over time or how missing values were treated in any analysis.

The primary population is described as participants who received >=1 dose of study medication, but analysis populations for the remaining outcomes are not reported in the registry record. The record also does not report a participant flow accounting for exclusions or missing outcome data. These details matter because outcome counts and summaries depend on who was included and how incomplete observations were handled. Without those methods and denominators, readers should avoid inferring completeness or assuming the same analysis population for every outcome.

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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: respiratory failure (14.3%), tachycardia (9.1%), multi-organ failure (7.1%), brain herniation (7.1%), blood bilirubin increased (7.1%).

The serious adverse-event figures are presented by age cohort, with the number at risk and the number affected listed for each cohort. The counts are 44 of 130 adults, 1 of 7 infants, 2 of 11 children aged 1 to <2 years, 0 of 12 children aged 2 to <6 years, 8 of 27 children aged 6 to <13 years, and 4 of 14 adolescents aged 13 to <18 years. The registry also lists other adverse-event counts by the same cohorts.

The serious-event terms include respiratory failure at 14.3%, tachycardia at 9.1%, and multi-organ failure, brain herniation, blood bilirubin increased, and cyclic vomiting syndrome at 7.1% each. These percentages are listed term frequencies; the registry record does not clarify their denominator in the information. They should not be read as treatment-attributable risks or compared across terms as if the underlying groups and methods were necessarily equivalent.

Serious adverse events are not the same endpoint as the primary outcome, which counts participants with any adverse event considered related to study treatment. The registry record does not report the primary outcome result. Death counts are not reported in the registry record. In general, adverse-event listings describe occurrences within a study; a single-arm study cannot determine how many would have occurred absent treatment.

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

The study contributes descriptive safety information about intravenous zanamivir use in hospitalized participants with confirmed influenza. Its registry record identifies a phase 2, open-label, single-arm design and lists adverse-event observations across age cohorts. The event listings provide a record of what was reported among participants in the study, including serious-event counts and selected serious-event terms.

These observations do not establish that zanamivir caused an event. The adverse-event definition includes occurrences temporally associated with use of a medicinal product, and the primary endpoint further relies on investigator assessment of relatedness. Even an investigator-assessed relationship is not equivalent to a randomized comparison that isolates a treatment effect. The study has no concurrent control group to show how frequently the same events occurred under another treatment or without zanamivir.

The registry record does not report the result for the primary endpoint, the number of participants with any adverse event considered related to treatment. The serious and other adverse-event figures do not substitute for that endpoint because they are presented as separate categories. The record also does not report confidence intervals or other uncertainty estimates for these results, so the precision of the reported counts cannot be characterized through an interval estimate.

The study lists secondary outcomes concerning virologic measures and clinical status, but the registry record does not report analyses for them. Their presence as outcome measures should not be taken as evidence that a particular finding was observed. Overall, the record supports a bounded interpretation: it documents a single-arm safety study and its posted cohort-level event listings, while leaving the primary treatment-related event result, comparative effects, and analysis details unreported. It does not establish efficacy or comparative safety.

14. Why This Trial Matters Statistically

This trial illustrates an important distinction in biostatistics: a study can be designed to collect safety information without being designed to estimate a comparative treatment effect. Its single-arm, open-label structure aligns with a descriptive safety objective, but it limits what can be concluded about whether events were more or less common because of the intervention.

The endpoint definition also matters. The primary outcome is not simply every event recorded; it is the number of participants whose adverse event was judged by an investigator to be related to treatment, over a stated follow-up period. Serious adverse-event counts and other adverse-event counts are separate listings. Keeping these definitions distinct prevents one safety summary from being mistaken for another.

The record shows why outcome listings and analysis results are different kinds of information. It names 34 outcome measures but lists zero analyses, and it does not report a result for the primary endpoint. A defined outcome indicates what was intended to be measured; it does not itself provide an estimate, uncertainty interval, or evidence of a treatment effect.

For clinical researchers, the key statistical lesson is to match the strength of an interpretation to the design, endpoint, population, and analysis that are actually reported. Descriptive cohort counts can be valuable safety observations, particularly in a study including age groups from infants through adults. They cannot replace a controlled comparison, and missing analysis details limit appraisal of precision and completeness. The registry record therefore offers useful context for interpreting safety reporting while also showing the boundaries of what the design and posted results can establish.

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.

The most important design limitation is the absence of a concurrent control group. Since the study is single-arm and non-randomized, event counts cannot be compared directly with outcomes under another treatment. Open-label conduct also means treatment was not masked; the registry does not describe procedures that might reduce the influence of treatment knowledge on investigator assessments of relatedness.

The primary outcome result is not reported in the registry record. The age-cohort serious and other adverse-event counts do not answer that primary treatment-related question. The record does not report confidence intervals, p-values, or other measures of precision, and it does not provide analysis methods for the listed outcomes. This prevents evaluation of the statistical uncertainty and prevents reconstruction of the reported primary analysis.

Although enrollment is listed as 202, the record does not provide a participant flow or a single primary-outcome denominator. It defines the safety population as participants who received >=1 dose, but does not report missing-data handling or explain whether analysis populations differed by outcome. Details of outcome adjudication beyond investigator assessment are not reported in the registry record.

The study lists 34 outcome measures and zero analyses. Multiplicity procedures, the distinction between confirmatory and exploratory outcomes, and the analysis plan are not reported. The record also does not report the sample-size justification. These limitations do not invalidate the descriptive counts, but they restrict what can be inferred about causation, comparative safety, precision, and completeness.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety Study to Assess IV Zanamivir for Treatment of Influenza Infection in Patients Who Are in Hospital — NCT01014988.
• Registry record last updated 2017-03-28; status last verified 2017-01.
• Results first posted 2017-03-28.
• 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

NCT01014988 is a completed phase 2, open-label, multi-center, single-arm study sponsored by GlaxoSmithKline. It enrolled 202 participants and evaluated intravenous zanamivir in hospitalized adults, adolescents, and children with confirmed influenza. The registry lists a start of 2009-11 and primary completion of 2015-02.

The primary outcome is the number of participants with any adverse event considered related to study treatment, among participants who received >=1 dose, up to post-treatment (PT) + 23 days. The registry record does not report the primary outcome result. Serious and other adverse-event counts are listed by age cohort, but the study has no randomized control group, so those figures are descriptive rather than comparative. The record lists 34 outcome measures and zero analyses; analysis methods, multiplicity handling, and missing-data methods are not reported in the registry record.