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 Efficacy of a Plant-derived Quadrivalent Virus-like Particle (VLP) Vaccine in the Elderly (NCT03739112), a randomized phase 3 study. The primary outcome is Number of Occurrences of Protocol-Defined Influenza-Like Illness (ILI) Due to Any Laboratory-Confirmed Influenza Strains.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03739112 |
| Phase | Phase 3 |
| Condition | Virus Diseases, RNA Virus Infections, Respiratory Tract Diseases |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 12794 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Medicago |
| Results posted | Yes |
2. Clinical Question
Population
Adults aged 65 years and older who participated in a Phase 3 study during the 2018–2019 influenza season. The primary endpoint was analyzed in the per-protocol set, defined in the registry record by participation through at least the end of the peak period, for at least five months, or through the end of surveillance.
Intervention
One intramuscular injection of 0.5 mL of Quadrivalent VLP Influenza Vaccine, described as 30 μg per strain, on Day 0.
Comparator
One intramuscular injection of 0.5 mL of Fluarix Quadrivalent comparator vaccine, described as 15 μg per strain, on Day 0. The trial used an active comparator rather than an untreated control.
Primary question
How did the number of protocol-defined influenza-like illness cases caused by any laboratory-confirmed influenza strain compare between the VLP vaccine and the active comparator, from Day 14 after vaccination through approximately nine months? The registry record also reports a sponsor analysis expressed as vaccine efficacy with a 95% confidence interval.
3. Trial Design
This was a randomized, observer-blind, active-comparator-controlled, multicenter Phase 3 study with a parallel-group design and quadruple masking recorded in the registry. It evaluated a plant-derived quadrivalent virus-like particle influenza vaccine in adults aged 65 years and older. The study status is completed. The registry records enrollment of 12,794 participants.
Participants were assigned to one of two vaccine groups. The VLP group received one 0.5 mL intramuscular dose described as 30 μg per strain. The comparator group received one 0.5 mL intramuscular dose of Fluarix Quadrivalent described as 15 μg per strain. Both injections were scheduled for Day 0. The study description identifies the 2018–2019 influenza season as the period of interest and says the study was intended to assess relative efficacy against a licensed vaccine.
The brief study description states that one dose of either vaccine was to be administered to 12,738 participants, while the registry enrollment is 12,794. These are different registry figures and should not be treated as interchangeable: enrollment describes the recorded study total, while the brief description states the intended number in its summary.
The primary endpoint counts protocol-defined influenza-like illness cases caused by any laboratory-confirmed influenza strain, assessed by RT-PCR. The primary analysis population was the per-protocol set, with eligibility described in the endpoint record. The registry lists 27 outcome measures and 26 posted secondary outcomes. Details about the randomization procedure, allocation concealment, site structure, protocol deviations, and the statistical analysis plan are not reported in the registry record.
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: Participants aged 65 years or older with no acute or evolving medical problems were assessed.
Overall Study
| Stage | Quadrivalent (30 μg) VLP Vaccine | Active Comparator (Fluarix) |
|---|---|---|
| STARTED | 6396 | 6398 |
| Vaccinated | 6365 | 6373 |
| COMPLETED | 6196 | 6222 |
| NOT COMPLETED | 200 | 176 |
Reasons for not completing this period:
| Reason | Quadrivalent (30 μg) VLP Vaccine | Active Comparator (Fluarix) |
|---|---|---|
| Adverse Event | 2 | 2 |
| Withdrawal by Subject | 38 | 19 |
| Lost to Follow-up | 31 | 33 |
| Protocol Deviation | 12 | 9 |
| Physician Decision | 1 | 0 |
| Death (Classified as Withdrawn from the Study by the Investigator as a Result of Death) | 12 | 16 |
| Site went on hold | 65 | 67 |
| Other than specified | 8 | 5 |
| Randomized but not vaccinated | 31 | 25 |
Analysis population for the primary outcome, as defined in the registry: The Per protocol (PP) set consisted of the participants who participated in the study until at least the end of the peak period or for at least five months or until the end of the surveillance 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.
Population: The Safety Analysis Set (SAS) was defined as all participants who received either the Quadrivalent VLP Influenza Vaccine or the active comparator. Participants that were non-compliant to protocol/Good Clinical Practice (GCP), as per investigator, were excluded from analysis.
| Characteristic | Unit | Quadrivalent (30 μg) VLP Vaccine | Active Comparator (Fluarix) | Total |
|---|---|---|---|---|
| Participants analysed | 6352 | 6366 | 12718 | |
| Age, Continuous | years | 72.2 (SD 5.67) | 72.2 (SD 5.70) | 72.2 (SD 5.69) |
| Sex: Female, Male: Female | Participants | 3552 | 3561 | 7113 |
| Sex: Female, Male: Male | Participants | 2800 | 2805 | 5605 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 202 | 195 | 397 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 6135 | 6161 | 12296 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 15 | 10 | 25 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 19 | 13 | 32 |
| Race (NIH/OMB): Asian | Participants | 305 | 299 | 604 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 5 | 5 | 10 |
| Race (NIH/OMB): Black or African American | Participants | 248 | 265 | 513 |
| Race (NIH/OMB): White | Participants | 5767 | 5773 | 11540 |
| Race (NIH/OMB): More than one race | Participants | 6 | 10 | 16 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 2 | 1 | 3 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Occurrences of Protocol-Defined Influenza-Like Illness (ILI) Due to Any Laboratory-Confirmed Influenza Strains, measured over Day 14 (post-vaccination) up to ~9 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Number of cases |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the number of occurrences of protocol-defined influenza-like illness caused by any laboratory-confirmed influenza strain. Laboratory confirmation was assessed using reverse transcriptase polymerase chain reaction, or RT-PCR. The registry defines an illness episode using a combination of respiratory and systemic symptoms: at least one listed respiratory symptom and at least one listed systemic symptom were required. The respiratory symptoms include sore throat, cough, sputum production, wheezing, or difficulty breathing; the systemic symptoms include fever, chills, tiredness, headache, or myalgia. The registry’s fever definition includes a temperature > 37.2 °C or > 99.0 °F.
The endpoint period began on Day 14 after vaccination and continued through approximately nine months. Counting laboratory-confirmed illnesses gives the trial a clinically interpretable measure of influenza-like illness while requiring evidence of influenza infection rather than relying on symptoms alone. Including any laboratory-confirmed influenza strain makes this endpoint broader than the separate posted outcomes concerning vaccine-matched strains.
The endpoint was evaluated in the per-protocol population. The registry describes this population by participation through at least the end of the peak period, for at least five months, or through the end of surveillance. The exact participant-level rules, handling of multiple episodes, and any further details about the primary endpoint analysis are not reported in the registry record. The reported case counts therefore describe the recorded endpoint in the stated analysis population, not necessarily every randomized participant.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary endpoint counts were 118 cases among 5,996 participants in the Quadrivalent VLP Vaccine group and 130 among 6,026 participants in the active comparator group. These are case counts, not percentages, and the denominators are the per-protocol analysis groups recorded for this endpoint. The raw counts alone do not express the sponsor’s efficacy analysis or establish the result of a non-inferiority test.
The sponsor-reported analysis gives vaccine efficacy of 8.8, with a 95% confidence interval from -16.7 to 28.7. The interval includes values below and above zero. In general, a confidence interval describes a range of effect estimates compatible with the data and the analysis assumptions; a broad interval indicates limited precision. Here the interval includes both an effect in the direction of lower efficacy and one in the direction of higher efficacy, so the point estimate should not be read in isolation.
The registry labels the sponsor analysis as non-inferiority, but the non-inferiority margin and the formal decision rule are not reported in the registry record. Without those details, the interval cannot by itself establish whether a prespecified non-inferiority criterion was met. No sponsor p-value is posted for this analysis. The registry also does not provide a method name for the sponsor’s analysis or a detailed account of its assumptions.
The primary endpoint is a count of illness occurrences rather than a binary outcome that simply records whether each participant ever had an illness. The registry counts are therefore not sufficient to reconstruct a participant-level risk comparison: the record does not provide all information needed to determine whether any participant contributed more than one occurrence or how repeated events were handled. The sponsor’s posted efficacy estimate and confidence interval are the relevant reported comparison for this endpoint.
These results concern the stated per-protocol population, endpoint definition, follow-up period, and active comparator. They should not be extended automatically to other populations, influenza seasons, endpoints, or comparisons. The registry entry contains no basis for interpreting the result as a medical recommendation.
9. Statistical Methods Explained
Clinical trial results can be reported in several forms, and those forms answer related but distinct questions. The primary endpoint is a count of influenza-like illness occurrences, while the sponsor’s reported comparison is expressed as vaccine efficacy with a confidence interval. The registry’s posted counts and the sponsor’s analysis should therefore be read as different components of the result, rather than assuming that the count difference itself is the reported efficacy estimate.
What does a confidence interval communicate?
In general, a confidence interval represents uncertainty around an estimated effect under the statistical model and assumptions used to calculate it. A narrower interval indicates greater precision; a wider interval indicates that the data are compatible with a wider range of values. The sponsor’s interval runs from -16.7 to 28.7 around the reported vaccine efficacy estimate of 8.8. Since this range includes values on both sides of zero, the estimate is not precise enough to rule out effects in either direction using the interval alone. The interval is reported at the 95% level.
A confidence interval is not a direct statement about the probability that the true effect lies inside that particular interval. It also does not show whether a non-inferiority criterion was met unless the criterion and its margin are known. The registry labels the analysis non-inferiority, but the margin and decision rule are not reported in the registry record. Consequently, the posted interval should be described as the sponsor’s estimate and uncertainty range, not as a stand-alone proof of a non-inferiority conclusion.
Why does the endpoint form matter?
The primary outcome is recorded as a number of occurrences. Counts can reflect both how many participants experience illness and whether some participants experience more than one episode. The registry lists 118 cases and 130 cases in the two per-protocol groups, but does not report participant-level event histories or a statistical model for the sponsor comparison. A simple comparison of the counts would not account for any unreported repeated events, differing follow-up, or the sponsor’s analysis choices. For that reason, the registry’s reported efficacy estimate and confidence interval are the main inferential results to quote.
For binary secondary outcomes, a risk difference compares the event proportions between groups. The recalculated risk differences and confidence intervals in the secondary analyses are unadjusted comparisons based on posted summary counts. A risk difference of zero represents equal proportions under that measure. A confidence interval that crosses zero includes both directions of difference under the calculation. These estimates are useful descriptive comparisons, but they do not substitute for a prespecified trial analysis, particularly when many outcomes are examined.
What does recalculation mean?
Recalculated results are simple, unadjusted re-calculations from posted summary statistics. They are not a reconstruction of the sponsor’s full analysis and do not incorporate information that is absent from the registry record. Where a sponsor analysis is reported for an endpoint, the sponsor’s own analysis takes precedence over an unadjusted calculation based on summary counts. For the primary endpoint, the registry includes a sponsor-reported efficacy estimate and confidence interval, and the discrepancy flag is false. No recalculated primary comparison is presented in place of that analysis.
The secondary endpoint calculations use the recorded group counts and denominators. They do not establish causality by themselves, and their nominal p-values do not account for the number of outcomes considered. Unadjusted p-values assess each comparison separately under its calculation assumptions. With multiple outcomes, the chance of at least one apparently unusual result can increase; multiplicity procedures are intended to address that issue. A multiplicity adjustment is not reported in the registry record, so the recalculated secondary p-values should be treated as exploratory rather than as a collection of confirmatory findings.
How should sample-size illustrations be read?
Sample-size illustrations based on observed effects describe hypothetical planning requirements under stated assumptions. The registry’s planning assumptions use a two-sided significance level of 0.05, equal allocation, and a normal approximation; the illustrated effect is a stated fraction of the observed effect. For binary endpoints, the listed quantities are participants per arm. These are planning illustrations, not observed trial power, and they are not the trial’s own sample-size justification. The protocol’s sample-size calculation and its assumptions are not reported in the registry record. An observed effect can be unstable, so planning from it should not be treated as a guarantee of future precision or as evidence that the original trial had a particular power.
Interpretation also depends on the analysis population and missing-data handling. The primary endpoint is reported for a per-protocol set with a registry definition based on study participation duration. The registry does not provide a full account of exclusions, missing endpoint observations, censoring, or sensitivity analyses. Such information matters because the composition of an analysis population can affect the estimated comparison. The posted record supports description of the reported analysis, but not assumptions about unreported statistical choices.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| not stated | percent VE 8.8 | -16.7 to 28.7 | not reported |
The sponsor’s posted primary analysis reports vaccine efficacy of 8.8 with a 95% confidence interval from -16.7 to 28.7 and labels the analysis non-inferiority. The registry does not post a p-value or the method used for this comparison. It also does not state the non-inferiority margin or the decision rule, so the sponsor’s label cannot be independently checked against a stated margin using the registry entry alone.
The primary endpoint counts are 118 in the VLP group and 130 in the active comparator group, with per-protocol denominators of 5,996 and 6,026. Those counts provide context, but a simple calculation from them would not necessarily reproduce the sponsor’s analysis. The endpoint is a count of occurrences, and the registry does not describe all participant-level data or analytic details needed to recreate the reported efficacy estimate.
The discrepancy flag is false, and the sponsor analysis is the reported primary comparison. Accordingly, it takes precedence over any simple unadjusted re-calculation from posted summary statistics. The point estimate and confidence interval should be read together, with the uncertainty and the missing non-inferiority details kept explicit.
11. Multiplicity, Missing Data and Analysis Populations
Multiplicity is relevant because the registry lists 26 secondary outcomes in addition to the primary outcome. When multiple hypotheses are tested, interpreting every unadjusted p-value as if it were the only test can overstate the strength of evidence. An adjustment or a prespecified testing hierarchy can control the interpretation of a family of comparisons, but neither an adjustment procedure nor a hierarchy is reported in the registry record. The posted secondary recalculations are unadjusted, so their p-values should not be read as multiplicity-controlled confirmatory evidence.
The registry identifies the primary analysis population as the per-protocol set. It defines this set by participation through at least the end of the peak period, for at least five months, or through the end of the surveillance period. The detailed operational rules, the number excluded from the primary analysis, and reasons for exclusions are not reported in the registry record. Enrollment and endpoint denominators are not the same recorded quantities, and the endpoint denominator should be used when describing the posted primary counts.
Missing-data handling is also not reported in the registry record. The entry does not explain how participants with incomplete follow-up, missing laboratory samples, or missing symptom information were handled, nor does it report sensitivity analyses evaluating alternative assumptions. These omissions limit assessment of how robust the result is to incomplete observation. They do not establish that missing data occurred or that a particular method was used.
Other statistical-plan details are not reported in the registry record, including the non-inferiority margin, the formal decision rule, the sponsor analysis method, any interim analyses, and the sample-size justification. The registry does label the primary analysis non-inferiority, but that label alone does not provide enough information to assess the prespecified criterion. The planning illustrations are explicitly based on observed effects and general assumptions; they should not be confused with the original design calculation.
12. 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 |
|---|---|---|---|
| Quadrivalent (30 μg) VLP Vaccine | 263 | 6352 | 4.1% |
| Active Comparator (Fluarix) | 266 | 6366 | 4.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Quadrivalent (30 μg) VLP Vaccine | 12 of 6352 |
| Active Comparator (Fluarix) | 17 of 6366 |
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 |
|---|---|
| Quadrivalent (30 μg) VLP Vaccine | 935 of 6352 |
| Active Comparator (Fluarix) | 908 of 6366 |
Most frequent serious adverse event terms
| Event term | Organ system | Quadrivalent (30 μg) VLP Vaccine | Active Comparator (Fluarix) |
|---|---|---|---|
| Pneumonia | Infections and infestations | 20 of 6352 | 11 of 6366 |
| Atrial fibrillation | Cardiac disorders | 11 of 6352 | 12 of 6366 |
| Osteoarthritis | Musculoskeletal and connective tissue disorders | 9 of 6352 | 9 of 6366 |
| Cerebrovascular accident | Nervous system disorders | 7 of 6352 | 9 of 6366 |
| Acute myocardial infarction | Cardiac disorders | 6 of 6352 | 8 of 6366 |
| Chronic obstructive pulmonary disease | Respiratory, thoracic and mediastinal disorders | 5 of 6352 | 6 of 6366 |
| Pulmonary embolism | Respiratory, thoracic and mediastinal disorders | 4 of 6352 | 6 of 6366 |
| Prostate cancer | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 3 of 6352 | 6 of 6366 |
| Transient ischaemic attack | Nervous system disorders | 6 of 6352 | 3 of 6366 |
| Coronary artery disease | Cardiac disorders | 5 of 6352 | 3 of 6366 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Quadrivalent (30 μg) VLP Vaccine | Active Comparator (Fluarix) |
|---|---|---|---|
| Nasopharyngitis | Infections and infestations | 88 of 6352 | 76 of 6366 |
| Headache | Nervous system disorders | 61 of 6352 | 66 of 6366 |
| Diarrhoea | Gastrointestinal disorders | 50 of 6352 | 53 of 6366 |
| Upper respiratory tract infection | Infections and infestations | 52 of 6352 | 47 of 6366 |
| Rhinorrhoea | Respiratory, thoracic and mediastinal disorders | 41 of 6352 | 56 of 6366 |
| Cough | Respiratory, thoracic and mediastinal disorders | 42 of 6352 | 46 of 6366 |
| Oropharyngeal pain | Respiratory, thoracic and mediastinal disorders | 47 of 6352 | 41 of 6366 |
| Myalgia | Musculoskeletal and connective tissue disorders | 32 of 6352 | 35 of 6366 |
| Hypertension | Vascular disorders | 35 of 6352 | 27 of 6366 |
| Nasal congestion | Respiratory, thoracic and mediastinal disorders | 29 of 6352 | 30 of 6366 |
Serious events with the highest arm-level rate: pneumonia (0.3%), atrial fibrillation (0.2%), osteoarthritis (0.1%), cerebrovascular accident (0.1%), acute myocardial infarction (0.1%).
The registry records serious adverse events in 263 of 6,352 participants in the Quadrivalent VLP Vaccine group and 266 of 6,366 participants in the active comparator group. It records other adverse events in 935 of 6,352 and 908 of 6,366 participants, respectively. Deaths are recorded for 12 participants in the VLP group and 17 in the comparator group. These are descriptive counts with the listed group denominators; they do not, on their own, establish why an event occurred or whether it was caused by vaccination.
The serious-event terms most frequently listed include pneumonia at 0.3%, atrial fibrillation at 0.2%, osteoarthritis at 0.1%, cerebrovascular accident at 0.1%, acute myocardial infarction at 0.1%, and transient ischaemic attack at 0.1%. The registry does not provide a causal attribution for these terms in the summary. Event counts and listed terms should be interpreted in the context of the study’s follow-up, population, and ascertainment methods; details about those methods are not reported in the registry record.
Comparisons of adverse-event counts are not equivalent to a complete safety assessment. The registry figures do not by themselves account for event timing, duration, severity beyond the reported categories, or underlying causes. They should be read as recorded events in each group, not as proof that one vaccine caused more or fewer events.
13. What the Result Does, and Does Not, Mean
The result describes a randomized comparison of a plant-derived quadrivalent VLP influenza vaccine with an active comparator in adults aged 65 years and older. For the primary endpoint, the registry reports 118 cases in the VLP group and 130 in the comparator group in the per-protocol population, alongside a sponsor-reported vaccine efficacy estimate of 8.8 and a 95% confidence interval from -16.7 to 28.7. The interval communicates substantial uncertainty and includes values on both sides of zero.
The registry labels the sponsor analysis non-inferiority, but it does not report the margin or formal criterion needed to assess that conclusion independently. The posted result therefore supports describing the estimate and its uncertainty, while leaving the formal non-inferiority decision unresolved from the registry record alone. A numerical point estimate should not be separated from its confidence interval or treated as an unqualified conclusion.
The endpoint is limited to protocol-defined influenza-like illness caused by laboratory-confirmed influenza strains, measured from Day 14 after vaccination through approximately nine months. It does not directly answer every question about influenza illness, other seasons, other populations, or outcomes beyond those recorded. The per-protocol analysis population also differs conceptually from an analysis of all randomized participants; the registry does not provide enough detail to evaluate the effect of exclusions or missing observations.
The secondary endpoints and safety counts provide additional descriptive information, but they do not change the primary endpoint definition. The secondary comparisons are unadjusted and numerous, so isolated nominal findings warrant caution. The adverse-event counts do not establish causal attribution. Overall, the registry record permits a careful account of what was measured and how uncertain the reported comparison is; it does not justify a broader claim about clinical benefit, harm, or performance outside the stated study conditions.
14. Why This Trial Matters Statistically
This trial illustrates why a registry result should be read at the level of its endpoint, population, and analysis rather than by comparing raw counts alone. The primary outcome is a count of laboratory-confirmed illness occurrences, and the sponsor reports a vaccine-efficacy estimate with a confidence interval. The counts give useful context, but they do not contain enough information to reproduce the sponsor’s analysis. Recognizing that distinction prevents a simple calculation from being mistaken for the trial’s reported inferential result.
The confidence interval is also central to the interpretation. The estimate is 8.8, but the interval from -16.7 to 28.7 spans values on either side of zero. That uncertainty matters especially because the record labels the analysis non-inferiority while omitting the margin and formal decision rule. A label without its prespecified criterion is not enough to determine whether the intended statistical standard was met.
The study also demonstrates the difference between a primary endpoint and a large set of secondary outcomes. Diverse secondary measures can offer context, but testing many outcomes without a reported multiplicity strategy weakens the confirmatory interpretation of isolated unadjusted findings. Sample-size illustrations derived from observed effects are similarly distinct from the original design justification and cannot be used as observed power.
Finally, the registry’s population and follow-up details shape what the result represents. The primary endpoint is analyzed in a per-protocol set over a defined surveillance period, while missing-data procedures and several analytic details are absent. Transparent interpretation therefore requires stating both the recorded result and what the registry does not document, rather than filling those gaps with assumptions.
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.
Several trial-specific details needed for a fuller appraisal are not reported in the registry record. These include the sponsor’s statistical method for the primary efficacy estimate, the non-inferiority margin and decision rule, the protocol’s sample-size justification, and any interim analyses. Without the margin, the non-inferiority label cannot be evaluated against a stated threshold from the registry entry alone.
The primary analysis uses a per-protocol population defined in the registry by participation duration. The record does not provide a full participant flow, detailed exclusion reasons, or an all-randomized analysis for the primary endpoint. It also does not report how incomplete follow-up, missing symptom records, or missing laboratory results were handled, or whether sensitivity analyses were performed. These details are important for assessing the potential influence of analysis-population choices and incomplete outcome ascertainment.
The primary outcome is reported as occurrences, but the registry does not specify in the result summary how repeated episodes within a participant were treated in the analysis or provide participant-level event data. The sponsor’s efficacy result therefore cannot be reconstructed from the posted group counts alone. The registry also does not provide enough information to evaluate differences in surveillance or follow-up between groups.
For secondary outcomes, the record lists many measures but does not report a multiplicity plan or confirmatory hierarchy. The unadjusted recalculations are consequently exploratory. Safety summaries provide counts and selected serious-event terms, but they do not by themselves establish causation or provide a complete account of event timing and clinical course. These limitations constrain interpretation of the registry record; they do not establish that any particular unreported method or event occurred.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Efficacy of a Plant-derived Quadrivalent Virus-like Particle (VLP) Vaccine in the Elderly — NCT03739112.
- Registry record last updated 2023-06-23; status last verified 2023-05.
- Results first posted 2023-06-23.
- 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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19. Record Summary
The registry describes a completed randomized, quadruple-masked, parallel-group Phase 3 study comparing a plant-derived Quadrivalent VLP influenza vaccine with Fluarix Quadrivalent in adults aged 65 years and older. Recorded enrollment is 12,794. Participants received one intramuscular dose on Day 0, with the VLP vaccine described as 30 μg per strain and the comparator as 15 μg per strain.
The primary endpoint was the number of protocol-defined influenza-like illness occurrences caused by any laboratory-confirmed influenza strain, assessed by RT-PCR from Day 14 after vaccination through approximately nine months. The per-protocol counts were 118 among 5,996 participants in the VLP group and 130 among 6,026 in the comparator group. The sponsor-reported vaccine efficacy was 8.8, with a 95% confidence interval from -16.7 to 28.7; the registry labels the analysis non-inferiority.
The registry does not report the non-inferiority margin, formal decision rule, detailed statistical method, multiplicity strategy, or missing-data handling. Secondary outcomes and adverse-event counts provide additional descriptive context, but should be interpreted with these limitations in mind.