Safety of One Dose of Meningococcal ACWY Conjugate Vaccine in Subjects From 2 Months to 55 Years of Age in the Republic of South Korea: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety of One Dose of Meningococcal ACWY Conjugate Vaccine in Subjects From 2 Months to 55 Years of Age in the Republic of South Korea (NCT01766206), a na phase 4 study. The primary outcome is Number of Subjects Reporting Any Local and Systemic Solicited Adverse Events (AEs).

2. Clinical Question

The study addressed the post-licensure safety monitoring of MenACWY-CRM (Menveo) when administered according to routine clinical practice and prescribing information to healthy subjects in South Korea aged 2 months to 55 years. Its main reported endpoint concerned whether participants experienced any specified solicited local or systemic adverse event during the period from Day 1 of vaccination to Day 7 post vaccination. The registry describes this as a post-marketing surveillance study and identifies continued safety evaluation in the Korean population as its purpose.

This is a descriptive safety question rather than a randomized treatment comparison. The registry record does not report a placebo group or another vaccine group, so the study cannot directly compare event frequency against an untreated or alternative-treatment control. The endpoint covers a defined list of symptoms and counts a participant if any listed symptom was reported, irrespective of intensity grade. The registry’s primary endpoint result is not reported in the registry record, so the frequency of this particular endpoint cannot be determined from the posted information.

3. Trial Design

This was a multicenter, single-arm, Phase 4 post-marketing surveillance study sponsored by GlaxoSmithKline. The record lists the study as completed and gives an enrollment of 3948. Its stated purpose was continued safety evaluation after licensure in the Korean population. The registry description says vaccination was administered according to routine clinical practice and prescribing information, rather than describing a randomized allocation process.

The study’s only listed group received MenACWY-CRM (Menveo). Allocation is recorded as not applicable, masking as none, and the model as single group. These design features matter when interpreting safety observations: there is no concurrent control group in the record against which event frequencies can be compared, and treatment assignment was not masked. The study therefore provides descriptive observations among vaccinated participants, not a randomized estimate of the difference between vaccination and another condition.

The registry lists the study start as 2013-03-15 and primary completion as 2018-01-22. The brief description identifies the surveillance as a post-licensure requirement of the Korea Food and Drug Administration. It says participants received the vaccine according to routine clinical practice and prescribing information. The record does not report further details about the recruitment process, the number or locations of participating centers, follow-up beyond the stated endpoint timeframe, or operational procedures used to collect safety information.

Enrollment is not necessarily the same as the number contributing to each outcome. For the primary endpoint, the population is described as a Safety per protocol set of enrolled subjects aged 2 months to 55 years who signed informed consent, underwent screening, received a subject number and study vaccination, and provided post-vaccination data. The population description then refers to excluding 19 subjects but does not complete the explanation in the registry record. The reported at-risk denominators for the adverse-event summaries are 3939.

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: Out of the 3,948 subjects enrolled, only 3,939 subjects were exposed to vaccination as 1 subject did not receive a study vaccination and 8 subjects did not provide post vaccination safety data. Among 3939 subjects, 15 subjects are in the ≥ 56 age category (outside the range defined as per the protocol).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: This analysis was performed on the Safety per protocol set, which included enrolled subjects aged from 2 months to 55 years, who signed an informed consent, underwent screening, received a subject number and received a study vaccination and provided post vaccination data. Excluding 19 subjects from safety set with protocol violations.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Subjects Reporting Any Local and Systemic Solicited Adverse Events (AEs), measured over From Day 1 of vaccination to Day 7 post vaccination.

The primary endpoint is the number of participants reporting any solicited local or systemic adverse event from Day 1 of vaccination to Day 7 post vaccination. The local symptoms listed are injection site erythema, injection site induration, injection site tenderness, and injection site pain. The systemic symptoms listed are change in eating habits, sleepiness, irritability, rash, vomiting, diarrhea, fever, chills, nausea, malaise, generalized myalgia, generalized arthralgia, and headache.

“Any” means at least one report of a specified symptom, regardless of intensity grade. The endpoint therefore counts participants, not the total number of symptom episodes. A participant reporting more than one listed symptom still contributes as a participant with an event under this definition. The outcome is binary at the participant level: a person either meets the definition or does not.

In general, a solicited endpoint uses a predefined symptom list and observation period so that safety monitoring is focused on specific events. Such an endpoint can describe the frequency of those events within the stated window, but it does not capture every possible health event or establish whether an event was caused by vaccination. The registry record does not report the primary endpoint’s observed participant count or frequency. It is therefore not possible to quantify the primary endpoint from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a participant count for a binary event definition. In general, a binary outcome records whether each participant meets a defined criterion, such as having at least one listed symptom during a specified interval. Summarizing such an outcome commonly involves a numerator—the participants meeting the definition—and a denominator—the participants assessed or at risk. The registry record gives neither a primary endpoint numerator nor its reported frequency, so no primary endpoint estimate can be described from the posted information.

What a participant count represents

For this endpoint, the unit is participants. “Any” combines the listed local and systemic symptoms into a participant-level indicator, irrespective of intensity grade. This differs from counting symptoms or episodes: one participant with several listed symptoms remains one participant for the endpoint count. The measure is useful for describing how many people reported at least one specified event within the defined window, while not conveying the number of events per person or the severity distribution.

The endpoint’s observation period runs from Day 1 of vaccination to Day 7 post vaccination. In general, the timeframe is part of the outcome definition: an event outside that interval is not part of this endpoint as described. The registry lists the symptoms to be assessed, but does not report the primary endpoint result, symptom-specific results for this endpoint, or a breakdown by age group. Those details are not reported in the registry record.

How to read the safety summaries

The adverse-event summary lists participant counts and at-risk denominators for serious and other adverse events. In general, a count should be interpreted together with its corresponding denominator because the denominator describes the population at risk for that summary. The posted serious-event figures are 8 participants out of 3939 at risk; the other-event figures are 1379 participants out of 3939 at risk. These summaries do not establish that the groups of participants are distinct, and they should not be added together. The registry does not report enough detail to determine overlap between categories.

In general, adverse-event summaries describe events observed during a study, while causal attribution requires additional information and analysis. The registry figures do not, by themselves, show that the vaccine caused an event. The record gives 0 deaths, but does not report a cause-of-death analysis because no deaths are listed. It also does not provide detailed event-level timing, duration, outcome, or relatedness assessments in the information described.

Design and statistical inference

The study is single group, has no masking, and lists allocation as not applicable. In general, a randomized comparison can help separate treatment differences from factors that influence both treatment choice and outcomes. A single-group surveillance study has no concurrent comparison arm, so counts describe the vaccinated participants but cannot establish how those counts compare with what would have occurred without vaccination or under another intervention. This is a design limitation, not a computational problem that can be resolved by re-expressing the same counts.

The registry lists zero analyses and does not report inferential results for the primary endpoint. No statistical analysis plan, model specification, confidence interval, p-value, or adjustment strategy is reported in the registry record. Therefore, a statistical significance interpretation is not available. In general, a p-value is a measure calculated under a specified statistical model and hypothesis; it does not directly measure clinical importance or establish causality. A confidence interval gives a range of values compatible with an estimate under its assumptions, but none is reported for the outcomes described.

Planning illustrations are not observed power

The planning assumptions describe an illustration based on an observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. The assumptions say that the effect to detect is a stated fraction of the observed effect. These are hypothetical planning conditions and do not describe the design of this single-group surveillance study. The study has no two-arm allocation in the registry record, and the primary endpoint effect needed for a numerical illustration is not reported in the registry record.

In general, sample-size planning asks how many participants would be needed to detect a specified effect under stated assumptions. It is distinct from observed power, which is not a useful substitute for an estimate and its uncertainty after data collection. A planning number does not show that the study was adequately powered, does not establish that an effect exists, and does not add a comparison group to a single-arm study. Numerical planning results are not described in the registry record.

For count outcomes based on time to event, planning may use different methods than for binary participant counts. The stated assumptions distinguish total event counts for time-to-event planning from participants per arm for other outcomes. That methodological distinction is general; the primary endpoint is described as a count of participants with a binary event, and the registry does not report a time-to-event analysis for it.

Over-dispersion and other model considerations

In general, over-dispersion occurs when observed variability exceeds what a statistical model assumes. It can make standard errors too small if ignored in settings where the model’s variance assumptions are not met. The registry information does not identify a count regression model or report an over-dispersion assessment, so this issue should not be treated as an analysis performed for this study. Here, the principal limitation is that the primary endpoint result and inferential analysis are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, while the described primary endpoint is the number of participants with any solicited local or systemic adverse event during the period from Day 1 to Day 7 post vaccination. The registry lists zero analyses. It does not report how the outcome measures were organized into primary and secondary hypotheses beyond the primary outcome description, whether formal hypothesis tests were planned, or whether any adjustment for multiple comparisons was intended. Those details are not reported in the registry record.

In general, multiplicity arises when several outcomes, timepoints, subgroups, or comparisons are tested. Repeated testing can increase the chance of at least one apparently unusual result even when no real effect exists. Approaches to multiplicity depend on the study questions and analysis plan. Because the registry does not report the analyses or an adjustment strategy, no conclusion can be drawn about how multiplicity was handled. The descriptive safety counts do not require an interpretation as a set of confirmatory hypothesis tests.

The primary endpoint population is described as the Safety per protocol set. It included enrolled subjects aged 2 months to 55 years who signed informed consent, underwent screening, received a subject number and study vaccination, and provided post-vaccination data. The record’s description then says “Excluding 19 subjects from” without completing the explanation. The reason for that exclusion and the resulting primary endpoint denominator are not reported in the registry record.

Missing-data methods are also not reported in the registry record. There is no description of how incomplete symptom diaries or other missing post-vaccination information were handled, whether participants with partial follow-up contributed to particular outcomes, or whether sensitivity analyses were conducted. In general, missing outcome information can affect estimates when participants with missing observations differ from those with complete data. The registry information does not allow assessment of whether that concern arose or how it was addressed. The primary endpoint count and its denominator are not given, preventing a detailed accounting of outcome completeness.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

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: pneumonia (0.1%), bronchiolitis (0.0%), tonsillitis (0.0%), pyrexia (0.0%), dizziness (0.0%).

The serious adverse-event summary lists 8 participants with serious adverse events among 3939 at risk in the MenACWY-CRM group. The summary lists 0 deaths. These are descriptive registry figures; they do not establish whether an event was caused by vaccination or how the observed frequency compares with an unvaccinated population or another vaccine group.

The top serious-event terms are pneumonia at 0.1%, and bronchiolitis, tonsillitis, pyrexia, and dizziness each at 0.0%. These are rounded percentages as displayed in the registry. In general, a rounded percentage of 0.0% does not necessarily mean there were no events; a small nonzero value can round to zero. Term-specific participant counts are not reported in the registry record, so the percentages should not be converted into counts.

The serious-event and other-event summaries are separate categories: the record lists 1379 participants with other adverse events among 3939 at risk. It does not report whether participants with serious events are also included in that other-event figure, nor does it define the “other” category in the information available. These counts should therefore be read separately, not combined. The record does not report detailed event timing, duration, outcomes, or relatedness assessments for these figures.

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

The posted information describes safety events observed in a completed, single-group, post-marketing surveillance study of MenACWY-CRM in healthy subjects aged 2 months to 55 years in South Korea. It reports 8 participants with serious adverse events and 1379 with other adverse events among 3939 at risk for each summary, and lists 0 deaths. It also gives rounded percentages for the most frequent serious-event terms. These are descriptive observations in the vaccinated group.

The primary outcome is defined as any specified solicited local or systemic symptom from Day 1 of vaccination to Day 7 post vaccination, regardless of intensity grade. Its result is not reported in the registry record. The available serious and other adverse-event summaries cannot fill that gap because they are not identified as the same endpoint, with the same symptom definitions and timeframe.

These results do not establish that vaccination caused any individual event. They also cannot establish a difference in event risk compared with no vaccination or another intervention because the registry describes a single group and no comparator. A count of observed events is not itself a causal estimate. Background health events, participant characteristics, timing, and other factors could matter, but the registry summaries do not provide the comparative data needed to separate these explanations.

The absence of reported primary endpoint estimates, confidence intervals, and analyses limits assessment of precision and statistical uncertainty. The serious-event percentages are rounded, and term-specific counts are not reported. Therefore, the numerical detail is not sufficient to evaluate rare-event precision or compare event rates across populations. No conclusion about efficacy is supported by these safety outcomes; the study’s stated purpose is safety surveillance, and the registry record does not provide an efficacy result.

In general, post-marketing surveillance can contribute information about events observed in clinical practice, while interpretation depends on how participants and outcomes were identified and followed. The registry record supports a description of the listed counts and design, but not a claim that the vaccine does or does not change the risk of those events.

13. Why This Trial Matters Statistically

This study is statistically notable for the distinction between safety surveillance and comparative evaluation. The registry describes a post-marketing, single-group study conducted in routine clinical practice, with enrollment of 3948 and a broad age range from 2 months to 55 years. Such a design can record events occurring after vaccination across the enrolled population, but it does not create a concurrent control group. The distinction is important: a descriptive event count answers what was recorded in the study group, not what would have happened to comparable people without the intervention.

The primary endpoint illustrates why outcome definitions and reporting completeness matter. It specifies a symptom list, a participant-level “any” definition, and a defined observation window. Those features clarify what the endpoint is intended to measure. However, the endpoint result itself is not reported in the registry record. Without the count and denominator, readers cannot assess its observed frequency or precision from the primary outcome description alone.

The other posted safety summaries add information, but they answer different questions. Serious adverse events and other adverse events are listed with denominators, while the primary solicited-event result is absent. Rounded term percentages also require care: a displayed 0.0% is not necessarily equivalent to no events. These examples show how a reader must distinguish an endpoint’s prespecified definition from broader safety categories and avoid treating rounded summaries as exact counts.

The record also highlights limitations in what registry entries can establish about analysis. It lists four outcomes and zero analyses, and does not report a statistical analysis plan, missing-data approach, or multiplicity procedure. Consequently, the posted information is best interpreted descriptively. It cannot support a reconstruction of unreported methods or a comparative causal conclusion. Clear reporting of denominators, event definitions, missingness, and uncertainty would be needed to make more detailed statistical judgments.

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 primary endpoint result is not reported in the registry record. Although its definition, timeframe, and intended population are described, the participant count and frequency are absent. The 1379 participants listed with other adverse events should not be treated as the primary endpoint result because the registry does not equate those outcomes or definitions.

The study is single group, with allocation recorded as not applicable and masking as none. There is no concurrent control arm in the registry record, limiting comparative interpretation and the ability to distinguish events associated with vaccination from events that might occur for other reasons. The reported counts are descriptive, not estimates of a treatment difference.

The primary population description is incomplete: it refers to excluding 19 subjects but does not state the reason or finish the sentence. The record identifies the Safety per protocol set criteria but does not give the primary endpoint denominator. Missing-data handling, follow-up completeness, outcome ascertainment procedures, and sensitivity analyses are not reported in the registry record.

The adverse-event summaries provide counts and at-risk denominators for serious and other events, but do not describe overlap between categories. For the listed serious-event terms, percentages are rounded and term-specific counts are not reported. Detailed information about event timing, duration, outcomes, and assessed relationship to vaccination is also not reported in the registry record.

Finally, the record lists four outcome measures and zero analyses. Statistical analysis methods, confidence intervals, p-values, subgroup analyses, and multiplicity handling are not reported. The posted information therefore does not permit assessment of statistical precision for the primary endpoint or a reconstruction of the study’s inferential approach.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Safety of One Dose of Meningococcal ACWY Conjugate Vaccine in Subjects From 2 Months to 55 Years of Age in the Republic of South Korea — NCT01766206.
• Registry record last updated 2018-09-21; status last verified 2018-07.
• Results first posted 2018-09-21.
• 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

The registry record describes a completed Phase 4, multicenter, single-arm post-marketing surveillance study sponsored by GlaxoSmithKline. It lists enrollment of 3948 and vaccination with MenACWY-CRM (Menveo) according to routine clinical practice and prescribing information in healthy subjects aged 2 months to 55 years in South Korea. Allocation is not applicable, masking is none, and the study model is single group.

The primary endpoint is the number of participants reporting any specified solicited local or systemic adverse event from Day 1 to Day 7 post vaccination. Its result is not reported in the registry record. The adverse-event summary lists 8 participants with serious adverse events and 1379 with other adverse events, each among 3939 at risk, and 0 deaths. The registry lists four outcome measures and zero analyses. The available results are descriptive and do not provide a controlled comparison or a causal estimate.