Oseltamivir Treatment for Children Less Than 24 Months of Age With Influenza: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Oseltamivir Treatment for Children Less Than 24 Months of Age With Influenza (NCT00391768), a non-randomized phase 1, phase 2 study. The primary outcome is Oseltamivir Carboxylate AUC12 (Area Under the Curve)..

2. Clinical Question

The study also addressed safety and pharmacokinetic questions. Listed secondary outcomes include adverse events, neurological events, serious adverse events, and relationships between viral RNA clearance and pharmacokinetic parameters. These objectives make the record relevant to understanding exposure and tolerability in the enrolled cohorts, but they do not establish how oseltamivir compares with an untreated or alternative-treatment group.

The registry summary describes a staged enrollment approach: older participants were to be enrolled first, with younger children enrolled after safety data for older participants were reviewed. That description explains the intended sequence, but the registry record does not report the review process or how it affected enrollment. The central statistical question is therefore descriptive: what exposure and safety findings were recorded in the treated cohorts, and how much detail is available to judge their precision?

3. Trial Design

This was a phase 1/phase 2 study with non-randomized allocation, no masking, and a parallel model. The registry reports enrollment of 87 and lists influenza as the condition. The sponsor was the National Institute of Allergy and Infectious Diseases. The recorded study start was 2007-01, the primary completion was 2010-03, and the status is completed.

All listed intervention information concerns oseltamivir (Tamiflu®). The study summary says children with confirmed influenza would receive the drug 2 times a day for 5 days. It describes blood sampling, nasal swabs, and body and nervous system evaluations, with study-related procedures lasting up to 37 days. These descriptions indicate a study focused on pharmacokinetic measurement and safety monitoring as well as viral outcomes.

The registry’s non-randomized allocation matters for interpretation. Cohorts are not randomly assigned to treatment conditions, and no like-for-like control comparison is described. The record itself cautions that the arms are not a comparable control contrast. Differences among cohort results, if examined, cannot automatically be attributed to treatment or age because the registry record does not report a randomized comparison or an adjustment strategy that would address such differences.

The primary endpoint was measured on day 3 of drug administration. Its defined population includes participants who received 3 days of study drug and had successful pharmacokinetic draws on that day. This is not necessarily identical to everyone enrolled. The registry record does not report the number included in this endpoint population, cohort-specific treatment doses, or a detailed analysis plan. The intended enrollment sequence based on age and safety review is described in the summary, but actual decision rules and their implementation are not reported in the registry record.

The record lists 8 outcome measures and 6 analyses. It also lists safety outcomes and analyses of correlations between viral RNA clearance and pharmacokinetic parameters. Those objectives broaden the study beyond the primary exposure endpoint, but the registry record does not provide enough detail to reconstruct the statistical procedures used for each outcome.

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.

Only the first 6 of 7 groups are shown.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects that received 3 days study drug administration and had successful PK draws on study day 3.

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 8 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Oseltamivir Carboxylate AUC12 (Area Under the Curve)., measured over Day 3 of drug administration.

The primary endpoint is oseltamivir carboxylate AUC12, described as an area under the curve and measured on day 3 of drug administration. The record says it was derived from a series of five blood draws over 10 to 12 hours. The endpoint population was participants who received 3 days of study drug and had successful pharmacokinetic draws on study day 3.

In general, an area-under-the-curve measure summarizes drug concentration across a sampling interval. It is used in pharmacokinetic studies because it represents exposure over time rather than a concentration at a single sampling moment. That can help characterize how drug exposure varies in a population and can inform evaluation of dosing. AUC is an exposure measure, not by itself a clinical outcome such as symptom improvement or prevention of complications.

The endpoint title and measurement description are reported, but the registry record does not report the observed AUC12 value, its variability, or a confidence interval. It also does not report a comparison of AUC12 across dose levels or against another treatment. The study summary describes an aim to learn about activity in the body and identify a dose that is safe, well-tolerated, and effective, but that aim should not be mistaken for a reported endpoint result. Without the observed estimate and its precision, the primary endpoint cannot be quantitatively interpreted from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary endpoint measure?

The primary endpoint is oseltamivir carboxylate AUC12 on day 3 of drug administration. The registry describes the measure as derived from five blood draws taken over 10 to 12 hours. In general, pharmacokinetic AUC represents drug exposure integrated across time. It differs from a single concentration because it incorporates multiple sampling points across an interval. The registry record does not report the numerical AUC12 estimate or a measure of its uncertainty, so the endpoint’s observed level and precision cannot be assessed from this record.

The endpoint is restricted to participants who received 3 days of study drug and had successful pharmacokinetic draws on study day 3. This definition identifies the intended analysis population, but the number meeting those conditions and the handling of incomplete or unusable samples are not reported in the registry record. The enrolled population and the endpoint population should not be assumed to be identical.

What does the design allow readers to compare?

The record identifies the study as non-randomized, unmasked, and parallel. It also cautions that the arms are not a like-for-like control comparison. In general, random assignment helps make groups comparable in expectation, while masking can reduce some forms of expectation-related influence on assessment. Neither feature is recorded for this study. The cohort data can be described, but they do not alone establish a causal contrast between treatments.

The study summary describes older participants as being enrolled first and younger participants after safety data for older participants were reviewed. This is a staged approach as described in the registry summary, not evidence that a particular statistical decision rule was followed. The registry record does not report the rules for progression between cohorts, any interim analyses, or how cohort results informed later enrollment.

How should event counts be read?

For binary outcomes, an event count records the number of participants with an event in a defined group. The registry’s safety record gives affected counts and at-risk counts by cohort. Such counts describe what was recorded in the specified groups; they do not establish that treatment caused an event. In general, counts are more informative when accompanied by clear event definitions, follow-up duration, and a description of how events were solicited and adjudicated. Those details are not fully reported in the registry record.

For the serious adverse event figures, the at-risk counts differ among cohorts. Small cohort counts can make estimates imprecise, and a count of zero does not establish that the underlying risk is zero. General statistical interpretation would account for uncertainty around event rates; the registry record does not report confidence intervals for these safety counts. The record also lists selected serious-event terms with percentages, but does not provide the full event-level context needed to interpret those terms as comparative risks.

What would a confidence interval add?

In general, a confidence interval expresses uncertainty around an estimate under the statistical method used. It helps readers distinguish a relatively precise estimate from one compatible with a broad range of values. For a pharmacokinetic endpoint, an interval around an AUC estimate would describe uncertainty in the estimated exposure; for an event rate, an interval would convey uncertainty in the rate. No confidence interval for the primary endpoint or the cohort safety counts is reported in the registry record.

What assumptions apply to planning illustrations?

The registry’s stated planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They say the effect to detect is a stated fraction of the observed effect. In general, sample-size planning illustrates what a future study might require under chosen assumptions; it is not an observed result and is not observed power. The stated assumptions are not a description of this trial’s design, which is non-randomized and does not provide a like-for-like control comparison. The registry record does not report the trial’s own sample-size justification or a power calculation.

Over-dispersion is a general concern when observed variability exceeds what a simple statistical model assumes. If that occurs, standard errors based on the simpler model may be too small and intervals or tests may convey too much certainty. The registry record does not identify the distributional model used for the primary endpoint or report a dispersion estimate, so it is not possible to determine whether over-dispersion was assessed or relevant to the sponsor’s analysis.

What analyses are not described?

The record lists 8 outcome measures and 6 analyses, including safety outcomes and correlations between viral RNA clearance and pharmacokinetic parameters. It does not report the specific statistical models, covariates, tests, confidence-interval methods, or analysis populations for these outcomes. A correlation can describe whether two measured quantities vary together, but it does not by itself show that one causes the other. The correlation results themselves are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 8 outcome measures and 6 analyses, including a primary pharmacokinetic endpoint and several secondary safety and viral-clearance questions. When multiple outcomes or analyses are considered, general statistical practice recognizes a multiplicity issue: the chance of at least one apparently notable finding can increase as more tests are conducted. A prespecified strategy may address this, for example by identifying a primary comparison or adjusting inference across tests. The registry record does not report a multiplicity adjustment or a hierarchy for interpreting the secondary outcomes.

Missing-data procedures are also not reported in the registry record. The primary endpoint population requires successful pharmacokinetic draws on study day 3, but the record does not state how many participants lacked successful draws, why data were missing, or whether any imputation or sensitivity analysis was used. It does not describe missingness for the secondary outcomes either. Because the primary endpoint population is defined by availability of successful draws, the endpoint result, if reported elsewhere, would need to be interpreted in light of who contributed usable data.

The registry identifies the primary endpoint population but does not fully describe analysis populations for the safety outcomes or the viral-clearance analyses. It is therefore not possible to determine from the registry record whether all enrolled participants were included in each analysis, how discontinuations were handled, or whether analyses followed a prespecified intention-to-treat or per-protocol principle. Those methods are not reported in the registry record.

The planning assumptions refer to equal allocation between two arms and a normal approximation, but this study is listed as non-randomized and does not have a like-for-like control comparison. The registry record does not report a sample-size justification for the trial. Any planning illustration based on an observed effect should be treated as hypothetical, not as an analysis of the trial’s achieved power.

11. 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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hypersensitivity (14.3%), viral upper respiratory tract infection (12.5%), oxygen saturation decreased (12.5%), respiratory distress (10.0%), influenza (8.3%).

The registry reports serious adverse event counts by cohort, alongside the number at risk. Cohort IA has 2 serious adverse events among 12 at risk; Cohort IB has 0 among 3; Cohort IIA has 1 among 7; Cohort IIB has 2 among 8; Cohort III has 2 among 24; Cohort IV has 1 among 10; and Cohort V has 0 among 23. These are counts in the recorded cohorts. They should not be interpreted as evidence that oseltamivir caused an event or as a comparison with an untreated group.

The registry also reports counts for other adverse events: Cohort IA has 8 affected among 12 at risk; Cohort IB has 1 among 3; Cohort IIA has 3 among 7; Cohort IIB has 6 among 8; Cohort III has 18 among 24; Cohort IV has 3 among 10; and Cohort V has 14 among 23. Serious and other adverse events are separate categories in the record and should not be conflated.

In general, event counts depend on the event definitions, observation period, and method of collection. The record lists secondary outcomes concerning events thought related to study therapy and events leading to discontinuation, but the cohort figures alone do not resolve causality or severity for each event. The registry record does not report confidence intervals for the counts or a comparative safety analysis.

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

The record shows that the study was designed to characterize oseltamivir carboxylate exposure and safety in children younger than 24 months with confirmed influenza. It defines a primary pharmacokinetic endpoint measured on day 3 and reports cohort-level adverse event counts. Those details describe the study’s objectives and selected recorded outcomes, but the primary endpoint’s observed value is not reported in the registry record.

The endpoint is a pharmacokinetic measure, not a direct measure of clinical recovery. In general, an AUC measure can characterize drug exposure over time. It may be useful in evaluating dosing, but it cannot by itself establish symptom benefit, reduced complications, or an overall clinical treatment effect. The registry record does not report a clinical efficacy estimate or a comparison against a control group.

The safety counts likewise do not show that treatment caused or prevented adverse events. The study is non-randomized and has no like-for-like control comparison. Cohort counts describe events recorded among participants at risk in each cohort; they do not supply a counterfactual estimate of what would have happened under another treatment or no treatment. Differences across cohorts should not be read as treatment effects.

The registry summary says the study aimed to learn about activity in the body and determine a dose that is safe, well-tolerated, and effective. That is a statement of purpose, not a reported conclusion. The available record does not provide the primary AUC result, its precision, results of the listed viral-clearance analyses, or a comparative clinical outcome result. It therefore does not support a conclusion about whether treatment works or does not work.

The most defensible interpretation is bounded: the record documents a completed pharmacokinetic and safety evaluation with staged cohorts, specified sampling, and reported adverse event counts. How precisely the primary exposure was estimated and what the full clinical or safety findings were are not reported in the registry record.

13. Why This Trial Matters Statistically

This study is statistically notable because its primary question concerns drug exposure in a population younger than 24 months, while its design is non-randomized and organized in parallel cohorts. The endpoint is pharmacokinetic rather than a direct clinical outcome. That distinction matters: exposure measurements can inform how a drug behaves in the body, but they answer a different question from whether a treatment changes symptoms or other clinical outcomes.

The endpoint definition also makes the analysis population important. Only participants who received 3 days of study drug and had successful day 3 pharmacokinetic draws meet the recorded primary-population definition. If that group differs from those without usable draws, the reported exposure estimate could describe a selected subset. The registry record does not report the number with successful draws or how missing measurements were handled, so this possible limitation cannot be evaluated further.

The staged enrollment description introduces another design feature relevant to interpretation. Older participants were to be enrolled before younger participants, with the latter enrolled after safety data for older participants were reviewed. In general, such sequencing can support cautious progression in early evaluations, but it also means that cohort composition and timing may differ. The actual review criteria and any statistical decision rules are not reported in the registry record.

The safety results illustrate why denominators and uncertainty matter. Cohorts have different at-risk counts, and several event counts are small. General statistical reasoning cautions against treating apparent differences in such counts as precise comparative effects, especially without randomization or reported uncertainty intervals. The registry record provides descriptive safety information, but not a controlled estimate of comparative risk.

Finally, the record names multiple secondary questions, including viral-clearance correlations, yet does not report their results or how multiple analyses were handled. This leaves the statistical interpretation focused on what was defined and counted, rather than on a complete set of inferential findings.

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 interpretation is that the registry record does not report the primary endpoint result. It gives the AUC12 definition, sampling description, and endpoint population, but no estimate, variability measure, confidence interval, or test result. Without those, the magnitude and precision of the pharmacokinetic finding cannot be assessed.

The study is explicitly non-randomized and has no like-for-like control comparison. Its cohort safety counts therefore do not provide a randomized estimate of treatment effects or comparative event risks. The record does not describe an adjustment method that would address differences among cohorts.

The endpoint population requires successful pharmacokinetic sampling after 3 days of treatment. The number of participants meeting that definition, reasons for missing or unusable samples, and missing-data methods are not reported in the registry record. These omissions limit assessment of how representative the endpoint analysis would be of those enrolled.

The registry describes staged enrollment, with older participants first and younger children after review of safety data, but does not report the review criteria, progression decisions, or any interim-analysis procedures. It also does not report a detailed statistical analysis plan, sample-size justification, multiplicity strategy, or methods for the listed correlation analyses.

Safety findings are presented as counts by cohort, without confidence intervals or the event-level context needed to assess causality. The record lists additional safety outcomes, but does not report their full results. As a result, the available registry information supports a limited descriptive account rather than a complete evaluation of exposure, efficacy, or comparative safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Oseltamivir Treatment for Children Less Than 24 Months of Age With Influenza — NCT00391768.
• Registry record last updated 2013-05-01; status last verified 2010-02.
• Results first posted 2011-06-20.
• 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

NCT00391768 is a completed phase 1/phase 2 study of oseltamivir in children younger than 24 months with confirmed influenza. The registry identifies the design as non-randomized, unmasked, and parallel, with enrollment of 87. The study summary describes treatment 2 times a day for 5 days and a staged sequence in which older participants were enrolled before younger participants.

The primary endpoint was oseltamivir carboxylate AUC12 on day 3, derived from five blood draws over 10 to 12 hours in participants who received 3 days of study drug and had successful pharmacokinetic draws. The observed endpoint result and its precision are not reported in the registry record.

Safety counts are reported by cohort, alongside at-risk counts. The record also lists secondary questions about adverse events and viral RNA clearance in relation to pharmacokinetic parameters, but does not report those analysis results in the information described. Since there is no randomized, like-for-like control comparison, the cohort data should be read descriptively rather than as comparative treatment effects.