This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Post-marketing Surveillance to Assess the Safety of Boostrix Vaccine Given According to Prescribing Information in Korea (NCT01929291), a registered phase not stated study. The primary outcome is Number of Unexpected Adverse Events (AEs).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01929291 |
| Phase | Phase not stated |
| Condition | Diphtheria-Tetanus-acellular Pertussis Vaccines |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 682 |
| Arms in the primary outcome | n/a |
| Lead sponsor | GlaxoSmithKline |
| Results posted | Yes |
2. Clinical Question
The study was designed to collect safety information after Boostrix vaccination in Korea under the approved prescribing information. Its primary question concerned the number of unexpected adverse events during the 30-day follow-up period after vaccination. An unexpected adverse event was defined as one not reflected in the approved prescribing information in Korea.
The surveillance was conducted in routine practice at a private clinic or hospital. The registry describes one Boostrix group spanning pre-adolescents, adolescents, adults and elderly participants. It does not describe a randomized or like-for-like control comparison, and allocation is not stated. The question is therefore descriptive: what safety events were recorded in the vaccinated cohort during the specified follow-up, rather than whether Boostrix differed from another intervention.
Population
Pre-adolescents aged 10 to less than 12 years, adolescents aged 12 to less than 19 years, adults aged 19 to 64 years, and elderly people aged 65 years or older in Korea. The primary analysis population was the Total Vaccinated cohort, defined as all subjects who received the study vaccine.
Intervention
Boostrix, administered according to the approved prescribing information in Korea as part of routine practice.
Comparator
No control group or comparative allocation is described in the registry record. The listed group is the Boostrix Group.
Primary question
How many unexpected adverse events, meaning events not reflected in the Korean prescribing information, were recorded during the 30-day period after vaccination?
3. Trial Design
This was a post-marketing surveillance study of Boostrix in Korea. The registry describes vaccine use according to the approved prescribing information and in routine practice at a private clinic or hospital. The study included one listed group, the Boostrix Group. No randomized allocation or control group is described; the allocation method is not stated. The data therefore describe safety after vaccination rather than a comparison between randomized treatment groups.
The registry lists enrollment of 682. The primary analysis population is described as the Total Vaccinated cohort, including all subjects who received the study vaccine. For the adverse-event entries, the record lists 672 at risk. These figures refer to differently labelled record entries; why they differ, and how the populations relate, is not reported in the registry record. The age categories were pre-adolescents aged 10 to less than 12 years, adolescents aged 12 to less than 19 years, adults aged 19 to 64 years, and elderly participants aged 65 years or older.
The primary outcome concerned unexpected adverse events during the 30-day period from Day 0 through Day 29 after vaccination. The record defines unexpected events as adverse events not reflected in the approved Korean prescribing information. It also records serious adverse-event information, including a serious-event count field and listed serious-event terms. The status is COMPLETED, with a start date of 2013-09-23 and primary completion date of 2016-01-11.
The registry record does not report additional sites, detailed recruitment procedures, eligibility criteria beyond the described age groups and vaccination setting, or a protocol-level account of follow-up procedures. It does not describe a control group, a prespecified statistical analysis plan, or whether any interim analyses were planned. Those omissions limit what can be inferred about how the surveillance was organized and how the posted safety information was 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
| Stage | Boostrix Group |
|---|---|
| STARTED | 672 |
| COMPLETED | 672 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: The analysis was performed on the Total Vaccinated cohort, which included all subjects who received the study vaccine.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Boostrix Group |
|---|---|---|
| Participants analysed | 672 | |
| Age, Continuous | Years | 44.38 (SD 14.76) |
| Sex: Female, Male: Female | Participants | 451 |
| Sex: Female, Male: Male | Participants | 221 |
| Race/Ethnicity, Customized: Korean | Participants | 672 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Unexpected Adverse Events (AEs), measured over During the 30-day (Day 0 - Day 29) follow-up period after vaccination..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Events |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the number of unexpected adverse events during the 30-day period after vaccination, covering Day 0 through Day 29. The registry defines an unexpected adverse event as one that is not reflected in the approved prescribing information in Korea. The analysis population is the Total Vaccinated cohort, described as all subjects who received the study vaccine. The endpoint is recorded in events, not as a comparative treatment effect.
In general, an event-count endpoint can describe the observed safety experience during a defined observation period. Its interpretation depends on what counts as an event, how events are identified and recorded, whether repeated events in one person are counted separately, and how much follow-up is available. Those details matter because an event count alone does not necessarily equal the number of affected participants. Apart from the endpoint definition and follow-up window, the registry record does not report these counting and ascertainment details.
The endpoint is relevant to post-marketing surveillance because it focuses on events not reflected in the local prescribing information. However, the registry record does not report the observed primary-endpoint count, an estimate of uncertainty, or a statistical analysis. It therefore does not allow a numerical conclusion about the frequency of unexpected events from this endpoint. The separate serious-event entries should not be treated as the primary-endpoint result: they are presented as safety information, and the record does not establish that the serious-event entries are identical to, or a subset of, the unexpected-event endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies a descriptive post-marketing safety question, but does not report the observed result for the primary endpoint. Although it defines unexpected adverse events and specifies the 30-day follow-up window, the number of such events, any measure of precision, and any statistical analysis are not reported in the registry record. As a result, the primary endpoint cannot be quantitatively interpreted from the registry information recorded.
Separate adverse-event entries list 672 at risk for the Boostrix Group, with 6 in the serious-event count field and 90 in the other adverse-event count field. The record also lists deaths as 0. These are the posted entries, not calculated rates. No proportions, confidence intervals, adjusted estimates, or comparisons should be inferred from them. In particular, the record does not explain whether these fields count events, affected participants, or both, so the entries should be read using their registry labels rather than reinterpreted as a count of unique people.
The serious-event terms listed include Vaginal haemorrhage at 0.3%, Gastroenteritis at 0.1%, Genital infection at 0.1%, Birth premature at 0.1%, and Fever at 0.1%. The registry record does not provide the event counts associated with these percentages, their calculation details, or information about overlap between terms. The percentages should therefore be quoted as recorded, without converting them into counts or treating them as comparative risks.
There is no control group described, and allocation is not stated. Consequently, the listed safety entries are not a basis for estimating a comparative effect or attributing an event to vaccination. In general, a safety event recorded after vaccination establishes timing, not causation; assessment of causality requires information and methods that are not reported in the registry record. Nor does the absence of a reported event count for the primary endpoint mean that no unexpected events occurred.
The record lists enrollment of 682, while the adverse-event entries list 672 at risk. The record does not explain the relationship between these counts. It is not appropriate to reconcile them by assumption. The registered completion status and dates describe the study record but do not supply the missing endpoint analysis. Overall, the available information supports a description of the study and a careful account of the recorded safety fields, but not a statistical estimate of the primary outcome or a comparative safety conclusion.
9. Statistical Methods Explained
The registry describes the primary outcome as a number of unexpected adverse events. This is a count outcome: it records how many qualifying events were observed, rather than a continuous measurement such as a laboratory value. The event definition and observation window determine what can enter the count. In this study, unexpected events are defined by whether they are reflected in the approved Korean prescribing information, and the stated period is Day 0 through Day 29 after vaccination.
What does a count endpoint tell the reader?
In general, a count can describe the observed event burden over a specified period. Its meaning depends on whether the count is of events or of people with at least one event. If a person can experience more than one event, an event count and a participant count are not interchangeable. The registry record gives the endpoint unit as events, but does not report how repeated events in the same participant were handled or how event reports were validated. Therefore, a reader should not interpret a count as the number of affected participants unless the record explicitly identifies it that way.
Counts are also influenced by how long participants are observed and by how completely events are captured. Here the primary outcome has a defined 30-day follow-up window, but the registry record does not report the detailed collection procedures, compliance with follow-up, or whether observation time differed between participants. General methods for count outcomes may account for differing exposure time, but no such analysis is reported for this study.
Why can count data be statistically challenging?
In general, simple count models often assume a particular relationship between the average count and its variability. If the observed variation is larger than that assumption allows, a phenomenon called over-dispersion, standard errors from a basic model may be too small and confidence intervals may be too narrow. Other features can also matter, including many zero counts, dependence between multiple events from one participant, and differing time at risk. These are general statistical considerations, not claims about the distribution in this study. The registry record reports no model, assessment of over-dispersion, or participant-level event distribution.
A confidence interval, in general, expresses the uncertainty around an estimated quantity under the assumptions of the analysis. A narrow interval indicates greater precision under those assumptions, while a wide interval indicates less precision. The registry record does not report a confidence interval for the primary endpoint or the method used to calculate one. No precision estimate can therefore be evaluated for that endpoint.
What do the planning assumptions mean?
The registry includes a planning illustration based on the observed effect. It describes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. These are assumptions for an illustrative planning calculation, not evidence that the trial itself used that design. The study record lists one Boostrix group and does not describe a randomized two-arm comparison. The illustration should not be read as the study's own sample-size justification or as observed power. No specific planning sample-size values are reported in the information available for this explanation.
In general, a planning sample size depends on assumptions about the effect to detect, variability, significance level, power, allocation, and analysis. Such calculations are conditional: changing assumptions changes the resulting planning requirement. They do not reveal the probability that a completed study has produced a true finding. Observed power is not a substitute for an estimate and its uncertainty. The registry record does not report a protocol-based sample-size justification or a power calculation for the primary endpoint.
What is known about the analysis?
The registry identifies the Total Vaccinated cohort as the primary analysis population and defines it as all subjects who received the study vaccine. It lists no analyses. This means that an analysis is not reported in the registry record; it does not establish that no analysis was performed outside the record. The record does not describe a statistical model, handling of missing observations, confidence-interval method, adjustment for covariates, subgroup analyses, or interim monitoring. No adjusted or recalculated estimate is available to distinguish from a sponsor analysis.
For a one-group surveillance study, the primary descriptive result could be expressed as a count, and a rate or proportion could be considered only with a clearly defined denominator and event unit. A comparison would require a suitable comparator and an analysis that addresses how groups were formed and followed. Here no comparator is described, so a comparative treatment estimate cannot be derived. General explanations of these methods do not imply that any was applied in this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists three outcome measures, but does not describe how they were prioritized beyond identifying the primary endpoint, or whether statistical testing was planned for any of them. It does not report a multiplicity strategy. In general, examining several outcomes or subgroups can increase the chance of finding an apparently notable result by chance if many tests are conducted. Methods such as prespecifying a primary outcome or adjusting inference can address that issue, but the record does not say whether such methods were used. No multiplicity-adjusted results are reported.
The primary analysis population is the Total Vaccinated cohort, defined as all subjects who received the study vaccine. The adverse-event entries separately list 672 at risk. The registry record does not explain how this at-risk group relates to the analysis population, or to the enrollment entry of 682. The relationship between these counts should not be inferred.
Missing-data methods are not reported in the registry record. It does not state whether participants who did not complete the 30-day follow-up were excluded, how incomplete event reports were handled, or whether any imputation or sensitivity analysis was performed. In general, missing follow-up can affect a safety summary if the chance of observing an event differs between participants with complete and incomplete follow-up. Without details on completeness and handling, the potential effect cannot be assessed.
The record also does not report subgroup analyses by age, interim analyses, or an analysis plan addressing multiple comparisons. These absences limit interpretation of how comprehensively the safety information was evaluated; they do not establish that such analyses were not performed outside the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Boostrix Group | 6 | 672 | 0.9% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Boostrix Group | 0 of 672 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Boostrix Group | 90 of 672 |
Most frequent serious adverse event terms
| Event term | Organ system | Boostrix Group |
|---|---|---|
| Vaginal haemorrhage | Reproductive system and breast disorders | 2 of 672 |
| Gastroenteritis | Gastrointestinal disorders | 1 of 672 |
| Genital infection | Reproductive system and breast disorders | 1 of 672 |
| Birth premature | Reproductive system and breast disorders | 1 of 672 |
| Fever | General disorders | 1 of 672 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Boostrix Group |
|---|---|---|
| Injection site Pain | General disorders | 21 of 672 |
| Constipation | Gastrointestinal disorders | 14 of 672 |
| Dyspepsia | Gastrointestinal disorders | 5 of 672 |
| Injection site Swelling | General disorders | 5 of 672 |
| Common cold | Respiratory, thoracic and mediastinal disorders | 4 of 672 |
| Labour premature | Reproductive system and breast disorders | 4 of 672 |
| Coughing | Respiratory, thoracic and mediastinal disorders | 4 of 672 |
| Injection site pruritus | General disorders | 3 of 672 |
| Injection site Mass | General disorders | 3 of 672 |
| Abdominal pain | Gastrointestinal disorders | 3 of 672 |
Serious events with the highest arm-level rate: vaginal haemorrhage (0.3%), gastroenteritis (0.1%), genital infection (0.1%), birth premature (0.1%), fever (0.1%).
The adverse-event record lists 672 at risk in the Boostrix Group, 6 in the serious-event field, 90 in the other adverse-event field, and 0 deaths. These are registry entries, not newly calculated rates. The record does not clarify whether the event fields count individual events, participants with events, or another unit, so they should not be recast as numbers of unique people.
The listed serious-event terms and percentages are Vaginal haemorrhage (0.3%), Gastroenteritis (0.1%), Genital infection (0.1%), Birth premature (0.1%), and Fever (0.1%). The record does not give their corresponding event counts, explain how the percentages were calculated, or indicate whether a participant could appear under more than one term. These terms should be read as the reported entries, not as a complete account of all safety events.
In general, an event occurring after vaccination does not by itself establish that vaccination caused it. The study has no described control group, and the registry record provides no causal assessment method. The serious-event information is descriptive and does not supply a comparative risk estimate.
12. What the Result Does, and Does Not, Mean
The record identifies a completed Korean post-marketing surveillance study intended to collect safety information after Boostrix vaccination according to the approved prescribing information. It specifies the population categories, routine-practice setting, vaccinated analysis population, primary event definition, and follow-up window. It also records selected adverse-event fields and serious-event terms. These details clarify what the surveillance sought to describe.
The primary endpoint result itself is not reported in the registry record. The number of unexpected adverse events during the 30-day period, along with a confidence interval or other measure of precision, is not available. The registry's adverse-event entries do not substitute for that endpoint result, and they cannot establish the frequency of unexpected events as defined for the primary outcome.
The record does not describe a control group or randomized allocation. The safety fields therefore do not answer a comparative question about Boostrix versus another vaccine, no vaccination, or another intervention. They also do not establish that an event was caused by vaccination. In general, interpreting safety observations requires context about event definitions, ascertainment, follow-up, and potential background occurrence; several of these details are not reported in the registry record.
The reported entries should be distinguished from unreported information. The record lists 6 in the serious-event field and 90 in the other adverse-event field among 672 at risk, and lists deaths as 0. It gives percentages for selected serious-event terms. It does not provide the associated counts for those terms, analysis details, or a reconciliation of enrollment of 682 with the adverse-event at-risk entry of 672. The available information supports describing what was recorded, but does not support calculating rates, making a causal claim, or drawing a comparative conclusion.
13. Why This Trial Matters Statistically
Post-marketing surveillance addresses safety in routine practice, where the purpose may be to collect information beyond the controlled conditions of a comparative trial. This record is useful for identifying the intended age groups, Korean clinical setting, definition of unexpected adverse events, and stated observation period. It also makes clear that the primary question is an event count in a vaccinated cohort, not an estimate of comparative efficacy.
Statistically, the distinction between a recorded count and an interpretable estimate is important. Counts need clear event definitions, ascertainment procedures, denominators, and follow-up information. Precision estimates help readers understand how much uncertainty surrounds a result. The registry record specifies the primary event concept but does not report its observed count or any measure of precision. It also does not explain the difference between enrollment of 682 and the at-risk entry of 672. These gaps limit quantitative interpretation even though the study's purpose and endpoint are described.
The record also illustrates why observed safety entries should not be confused with causal evidence. With no control group described, there is no like-for-like comparison in the registry information. The counts and listed terms can be read as descriptive entries, but not as a comparative effect or a causal estimate. The statistical contribution of a surveillance study depends not only on collecting events but also on reporting how they were counted, how complete follow-up was, and how uncertainty was assessed. Those analysis details are not reported in the registry record.
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.
A central limitation is that the registry record does not report the result for the primary endpoint. It defines unexpected adverse events and the 30-day observation window, but gives no endpoint count, estimate of precision, or statistical analysis. The primary safety question therefore cannot be answered quantitatively from the registry information.
The record lists enrollment of 682 and an adverse-event at-risk entry of 672. It does not explain the difference or define how the at-risk group was formed. The primary population is described as all subjects who received the vaccine, but its relationship to the adverse-event entries is not stated. No reconciliation should be assumed.
Only one group is described, and allocation is not stated. There is no like-for-like control comparison in the registry record. The adverse-event entries are consequently descriptive and cannot establish a comparative difference or attribute an event to vaccination. The record does not clarify whether the serious and other adverse-event fields count events or affected participants, nor does it give event counts corresponding to the listed serious-event percentages.
Other study-specific details are also absent: the registry record does not report event-ascertainment procedures, completeness of the 30-day follow-up, handling of missing data, subgroup analyses, multiplicity methods, an interim-analysis plan, or a protocol-based sample-size justification. It lists a planning illustration, but that is not a report of the study's design or observed power. These limitations concern what can be learned from the registry record; they do not establish that unreported procedures or analyses were not conducted elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Post-marketing Surveillance to Assess the Safety of Boostrix Vaccine Given According to Prescribing Information in Korea — NCT01929291.
- Registry record last updated 2019-09-25; status last verified 2019-09.
- Results first posted 2019-03-29.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT01929291 is a completed post-marketing surveillance study sponsored by GlaxoSmithKline. It assessed safety after Boostrix was administered according to the approved prescribing information in Korea. The registry lists enrollment of 682, a start date of 2013-09-23, and a primary completion date of 2016-01-11.
The study describes pre-adolescents, adolescents, adults, and elderly participants receiving the vaccine in routine practice. Its primary endpoint is the number of unexpected adverse events during Day 0 through Day 29 after vaccination, among the Total Vaccinated cohort. The endpoint result and statistical analysis are not reported in the registry record.
The adverse-event entries list 672 at risk, 6 in the serious-event field, 90 in the other adverse-event field, and 0 deaths. The record does not explain how these entries relate to the enrollment count or specify the event unit for each field. No control group is described, so the recorded information is descriptive rather than comparative.