Palivizumab for Prevention of Severe Respiratory Syncytial Virus Infection in Russian Children: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Palivizumab for Prevention of Severe Respiratory Syncytial Virus Infection in Russian Children (NCT01006629), a non-randomized phase 2, phase 3 study. The primary outcome is Frequency of Adverse Events.

2. Clinical Question

3. Trial Design

This was a prospective, multicenter, open-label, non-comparative study in the Russian Federation. The registry classifies it as phase 2 and phase 3, with non-randomized allocation, no masking, and a single-group model. The planned enrollment was 100 children. The status is completed; the recorded study start was 2009-11 and primary completion was 2010-04.

Participants were children of 2 years of age and less in high-risk populations, described as preterm and/or having heart or lung problems. The intervention was palivizumab, administered intramuscularly at 15 mg/kg every 30 days for 3 to 5 injections. Because everyone in the described study group received the intervention and there was no control group, the design can describe outcomes among treated participants but cannot directly estimate how those outcomes compare with outcomes under another treatment or no treatment.

The primary outcome was frequency of adverse events, expressed as the number of participants with an event. Its stated observation period was through 30 days following the last injection. The record’s outcome description defines treatment-emergent events as occurring after study-drug initiation and within 30 and 100 days after the last dose, and says the summarized primary measure concerns serious or nonserious events within 30 days after the last dose.

The registry also lists RSV hospitalization days, hospitalization days with increased supplemental oxygen requirement, intensive care unit admissions and stay, and mechanical ventilation during RSV hospitalization. The registry record does not report the protocol, eligibility criteria in more detail, or the planned statistical analysis. The number of analyses recorded is 0. Thus, the design and recorded outcome definitions can be described, but the record does not establish how all planned outcomes were to be analyzed.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

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 Frequency of Adverse Events, measured over Through 30 days following the last injection of palivizumab.

The primary endpoint is the frequency of adverse events, expressed as the number of participants who experienced an event. The description specifies treatment-emergent events: events occurring after study-drug initiation, with the summarized measure counting participants who experienced a serious or nonserious event within 30 days after the last dose. The listed timeframe is through 30 days following the last injection.

A participant count is a direct way to describe how many people in the treated group had an event during the defined observation period. The registry reports 100 participants at risk for the adverse-event summaries, with 10 affected by serious adverse events and 39 affected by other adverse events. These are descriptive counts in the palivizumab group, not comparisons between treatment groups. The record does not report a confidence interval or an inferential test for this endpoint.

In general, a safety endpoint can help characterize events observed during a specified treatment and follow-up period. Its interpretation depends on how events are defined, how completely they are collected, and which participants are included in the denominator. The registry identifies a 30-day primary summary and also mentions a 100-day period in its broader event definition; these periods should not be conflated. The primary endpoint concerns adverse events, not a direct estimate of prevention of RSV illness. The registry record does not report a primary efficacy result for preventing severe RSV infection.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The main outcome is binary at the participant level: a participant either experienced a qualifying adverse event during the defined period or did not. In general, a binary outcome can be summarized by counting participants with an event and identifying the number at risk. The record reports 100 participants at risk for the adverse-event summaries, with 10 affected by serious adverse events and 39 affected by other adverse events. These counts do not by themselves describe the number of separate events, the timing of each event, or the number of participants who may have experienced more than one type.

What does a participant count tell us?

A count is an absolute description of the observed group. It is useful for seeing how many participants were recorded as having an event, but interpretation depends on the denominator and on consistent event ascertainment. The registry gives the denominator for these summaries as 100 participants at risk. It does not provide participant-level records or further information about missing observations. No new rate or contrast is needed to interpret the reported counts, and none is estimated.

In general, an estimated event frequency is subject to sampling uncertainty: another group of participants from a similar population might have a different observed count. A confidence interval expresses a range of values compatible with the data under a specified statistical method and assumptions. The registry record does not report a confidence interval for the adverse-event summaries. It therefore does not quantify their precision beyond the observed counts. The absence of an interval is not evidence that the estimate is exact; it means that the posted record does not provide that measure of uncertainty.

Why does the design matter?

The study is classified as single-group, non-randomized, and open-label. In general, a randomized concurrent control group can support a direct comparison by helping distinguish differences between treatment groups from background event occurrence and other influences. Here, there is no comparator group. Consequently, the data describe events observed among participants receiving palivizumab, but they do not identify a comparative treatment effect. Open-label status also means masking is listed as none; the registry record does not report further procedures for outcome assessment.

The term treatment-emergent describes an event’s timing relative to study-drug initiation and the last dose. It is a temporal definition and should not be treated as proof of causation. The record says events were defined after initiation and within 30 and 100 days after the last dose, while the primary summary counts serious or nonserious events within 30 days after the last dose. Keeping the definition and the primary summary period separate is important when interpreting any safety count.

What can be inferred from the recorded analysis information?

The registry records 0 analyses. No p-value, confidence interval, model estimate, or adjusted analysis is reported for the primary outcome. Without such results, there is no inferential estimate to interpret. In general, a p-value addresses how compatible data are with a specified null model under its assumptions; it does not measure the size or clinical importance of an effect. A confidence interval conveys uncertainty around an estimate. Neither is available for the posted adverse-event counts.

The registry lists eight outcome measures, including the adverse-event outcome and RSV-related outcomes. Secondary outcomes include total RSV hospitalization days, hospitalization days with increased supplemental oxygen requirement, intensive care unit admissions and days, and use and days of mechanical ventilation during RSV hospitalization. The record does not report statistical methods or numerical results for these additional outcomes in the registry record for this analysis. Their listing alone does not establish that all were observed, analyzed, or reported.

How should the planning assumptions be read?

The planning description refers to illustrations computed from an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. In general, a sample-size calculation estimates how many participants a hypothetical study might require under specified assumptions. Such a calculation is not a measure of what happened in the completed trial, and a planning illustration is not observed power.

The assumptions describe a two-arm planning framework, whereas the actual study is a single-group, non-comparative study. The registry record does not report that this illustration was the study’s original design calculation or sample-size justification. The registry also does not report the protocol or statistical analysis plan, so further details about the intended tests, models, analysis populations, or handling of missing outcomes are not reported in the registry record.

For count outcomes, over-dispersion can matter in general when observed variation exceeds what a chosen probability model expects; a model that fails to allow for this can understate uncertainty. That issue is not a reported analysis feature of this study. The primary endpoint is a participant-level event count rather than a reported count of recurrent events, and no model for repeated events is documented. Statistical explanations of possible methods should not be mistaken for methods actually used in the registry analysis.

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("Palivizumab")
n      <- c(100)
events <- c(41)
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  Palivizumab  100  41  41.0  31.3  51.3  31.9  50.8  31.9  50.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists eight outcome measures, including the primary adverse-event outcome and secondary RSV-related outcomes. When a study evaluates multiple outcomes, general statistical practice may consider how repeated testing affects the chance of finding an apparently notable result. The registry record does not report a multiplicity strategy, such as an adjustment procedure or a hierarchy for interpreting outcomes. It also records 0 analyses, so there are no posted inferential results from which to assess how multiplicity was handled.

Information about missing data is not reported in the registry record. The record does not state how many participants completed follow-up, whether any outcome observations were missing, or how missing observations were handled. It does not describe an analysis population beyond the adverse-event denominator of 100 participants at risk. The registry record does not report whether all enrolled participants were included in every outcome summary or whether a particular population definition was used.

These omissions matter because outcome frequencies depend on who is included and how events are collected. In general, excluding participants with incomplete follow-up can affect a descriptive estimate if their event experience differs from that of participants with complete data. The record does not provide enough information to assess whether this issue arose or how it was addressed. It also does not report interim analyses, a prespecified statistical plan, or other analysis details; those items are not reported in the registry record.

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: bronchitis (4.0%), enteritis (3.0%), supraventricular tachycardia (1.0%), pneumonia (1.0%), tonsillitis (1.0%).

The registry reports 10 participants with serious adverse events and 39 participants with other adverse events, each among 100 participants at risk in the palivizumab group. The serious-event terms listed include bronchitis (4.0%), enteritis (3.0%), supraventricular tachycardia (1.0%), pneumonia (1.0%), tonsillitis (1.0%), and upper respiratory tract infection (1.0%). The listed term percentages are registry entries and should not be added together or treated as a count of distinct participants; the record does not provide information about overlap among terms.

The primary outcome description counts participants experiencing a serious or nonserious treatment-emergent event within 30 days after the last dose. The broader event definition also mentions events within 30 and 100 days after the last dose. The summaries are not a comparison with another group, and the term treatment-emergent does not establish that palivizumab caused an event. No confidence interval or statistical test is reported. These figures describe the registry’s safety summaries, but do not establish comparative risk or causal attribution.

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

The posted results provide a descriptive account of adverse events among participants who received palivizumab in this single-group study. The serious-event summary reports 10 affected participants among 100 at risk, and the summary for other adverse events reports 39 affected participants among 100 at risk. The registry also names several serious adverse-event terms with their recorded percentages. These observations can help characterize what was reported in this group during the specified follow-up, but their precision is not quantified by a confidence interval in the registry record.

The study’s design does not support a direct comparison with another treatment or with no treatment. Without a concurrent comparator, event counts cannot show whether the observed experience differs from what would have occurred otherwise. The open-label design and the absence of reported inferential analyses further limit what can be concluded from the registry summaries. Treatment-emergent timing should not be confused with proof that the drug caused an event.

The stated study purpose includes safety and efficacy in children at high risk of severe RSV infection. However, the primary outcome described is adverse-event frequency. Although RSV hospitalization, intensive care, oxygen, and ventilation outcomes are listed, numerical results for those outcomes are not reported in the registry record available for this analysis. The listed outcomes therefore cannot be used to quantify an efficacy effect from these registry entries.

The results do not establish that palivizumab prevents severe RSV infection, nor do they establish that it does not. They also do not establish comparative safety, because no control group is included. The appropriate interpretation is narrower: the registry records adverse-event counts and event terms in the treated group, while important comparative and inferential questions remain unanswered.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between describing outcomes and estimating a treatment effect. The study prospectively followed a single group of high-risk children receiving palivizumab, and the registry records counts of participants with adverse events. Those counts describe what was observed in the group. They do not, by themselves, indicate how outcomes would compare under another treatment or without treatment.

The non-comparative design is central to interpretation, not a technical detail that can be repaired by presenting event counts more precisely. A control group provides a basis for estimating a contrast; without one, background event occurrence and other influences cannot be separated from treatment-associated experience. The registry’s open-label classification and lack of reported inferential analyses also mean that the posted summaries do not support a causal or adjusted estimate.

The record illustrates why endpoint definitions and observation periods matter. The primary measure counts participants with adverse events within 30 days after the last dose, while the event definition also refers to a 100-day period. Distinguishing the outcome’s summarized timeframe from the broader definition prevents a reader from treating different follow-up windows as equivalent.

Finally, a study purpose that includes efficacy does not substitute for reported efficacy results. RSV hospitalization and related outcomes are listed, but numerical results are not reported in the registry record. The statistical contribution that can be interpreted from the registry entries is therefore a safety description in a treated group, alongside clear limits on comparative inference.

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 principal limitation is the single-group, non-randomized design. There is no comparator, so the registry results cannot estimate a difference between palivizumab and another treatment or no treatment. The open-label classification indicates that masking was none. The registry record does not report further details about outcome assessment or procedures that might affect event reporting.

The primary safety outcome is described as the number of participants with a serious or nonserious treatment-emergent event within 30 days after the last dose. The event definition also refers to events within 30 and 100 days after the last dose. This wording leaves a distinction between the broader event definition and the primary summary window that should be preserved when reading the results. The record does not provide participant-level timing or event-level detail.

Although the registry lists RSV hospitalization and other clinical outcomes, their numerical results are not reported in the registry record. The record does not provide confidence intervals, p-values, or inferential analyses, and it does not describe a statistical analysis plan. Information on missing outcomes, analysis populations, multiplicity, and interim analyses is not reported in the registry record.

The sample-size assumptions describe planning illustrations based on an observed effect and a hypothetical equal-allocation, two-arm framework. That framework is not the study’s single-group design, and the registry record does not report the study’s own sample-size justification. These limitations mean the posted safety counts can be described, but comparative effects, precision, and the handling of unreported outcomes cannot be assessed from the registry entry.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Palivizumab for Prevention of Severe Respiratory Syncytial Virus Infection in Russian Children — NCT01006629.
• Registry record last updated 2011-07-19; status last verified 2011-06.
• Results first posted 2011-07-19.
• 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

NCT01006629 is a completed, prospective, multicenter, open-label, non-comparative study of palivizumab in high-risk children in the Russian Federation. The registry classifies it as phase 2 and phase 3, with non-randomized allocation and a single-group model. Planned enrollment was 100. The recorded study start was 2009-11 and primary completion was 2010-04.

Participants received palivizumab 15 mg/kg intramuscularly every 30 days for 3 to 5 injections. The primary outcome was frequency of adverse events. The registry reports 10 participants with serious adverse events and 39 with other adverse events among 100 at risk, with several serious-event terms listed. It also lists RSV-related secondary outcomes, but their numerical results are not reported in the registry record. No statistical analyses are recorded, and there is no comparator group for estimating a treatment contrast.