Second Extension Study to Evaluate Safety and Tolerability of Influenza Vaccines in Adults and Elderly, and to Evaluate Immunogenicity and Concomitant Vaccination With Pneumococcal Vaccine in a Subgroup: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Second Extension Study to Evaluate Safety and Tolerability of Influenza Vaccines in Adults and Elderly, and to Evaluate Immunogenicity and Concomitant Vaccination With Pneumococcal Vaccine in a Subgroup (NCT00579345), a randomized phase 3 study. The primary outcome is Number of Randomized Participants Reporting Local and Systemic Reactions..

2. Clinical Question

3. Trial Design

This was a Phase III, randomized, single-blind, parallel-group, multicenter extension study. It enrolled 1522 participants and is recorded as completed. The study began in 2007-10, and primary completion was recorded as 2008-06. It concerned adults and elderly subjects who had participated in Study V58P4, with the study description emphasizing safety and tolerability of seasonal trivalent influenza vaccines.

The two influenza vaccines were cTIV, produced in mammalian cell culture, and eTIV a, an egg-derived seasonal trivalent vaccine described as thiomersal free. The study included vaccination with either influenza vaccine alone. In an elderly subgroup, it also evaluated concomitant administration with the 23-valent pneumococcal vaccine, PV. The registry records vaccine groups for adults and elderly subjects and separate elderly groups for influenza vaccination alone and concomitant vaccination.

The overall study aims covered safety and immunogenicity. The primary outcome was a count of randomized participants reporting local and systemic reactions, with a one-week postvaccination timeframe. The brief summary additionally describes immunogenicity and safety evaluation when influenza vaccine was administered alone or with PV in elderly subjects, and annual vaccination in adults and elderly subjects. Listed secondary outcomes include local and systemic reactions, antibody response assessed by hemagglutination inhibition assay, and a geometric mean ratio from Day 1 to Day 22 after a single influenza-vaccine dose.

The registry identifies randomized allocation and single masking, but the randomization procedure, allocation ratio, identity of the masked party, and operational details of the multicenter conduct are not reported in the registry record. The extension-study context is relevant: participants were not described as a wholly new population, but as people who had participated in Study V58P4. The record does not provide further details about the earlier study or how participation in it affected eligibility or analysis.

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: All subjects enrolled were included in the trial. The data entered is for overall study.

Only the first 6 of 8 groups are shown.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety set: this population consisted of all subjects who were vaccinated and who had some post-baseline safety data.

5. Baseline Characteristics

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

Only the first 6 of 9 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Number of Randomized Participants Reporting Local and Systemic Reactions., measured over One week postvaccination.

The primary endpoint is the number of randomized participants reporting local and systemic reactions. Its stated timeframe is one week after vaccination. The description identifies local reactions at the influenza vaccine injection site and characterizes the assessment as an evaluation of safety and tolerability after a single intramuscular injection. The primary-outcome population is described as the safety set, consisting of vaccinated subjects with some post-baseline safety data.

A count of participants reporting reactions is a binary-outcome summary at the individual level: each participant is classified according to whether a qualifying event was reported during the specified period. In general, this kind of endpoint can describe how often reactions occurred in a defined population. It does not, by itself, convey the severity, duration, or clinical significance of every reported reaction. Those details require the event definitions and more granular outcome data.

The registry record does not report numerical results for the primary endpoint, definitions or grading rules for local and systemic reactions, or the method used to combine or separately analyze those reaction categories. It therefore does not support a numerical comparison of primary-endpoint reaction counts between vaccine groups. The safety counts reported elsewhere in the record should not be treated as the primary endpoint unless their event definitions and analysis match the primary outcome; that match is not established in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

In general, a randomized parallel-group trial assigns participants to treatment groups and follows those groups for specified outcomes. Randomization can help balance participant characteristics across groups, on average, but its practical value depends on how allocation is generated, implemented, and maintained. The registry records randomized allocation, a parallel model, and single masking. The sequence-generation method, concealment procedures, and identity of the masked party are not reported in the registry record, so the full safeguards against selection or assessment bias cannot be evaluated from this record alone.

The primary endpoint is a count of participants reporting reactions, rather than a continuous measurement such as a laboratory value. For a binary outcome, a typical analysis compares the number of participants with an event against the number assessed in each group. The outcome definition, denominator, handling of multiple reactions in one participant, and statistical model all affect interpretation. Although the registry names the primary outcome and its one-week timeframe, the primary numerical results and these analytic details are not reported in the registry record.

In general, a confidence interval expresses uncertainty around an estimated effect under a particular analysis. A narrow interval indicates greater precision than a wide interval, while an interval that includes values on both sides of a no-difference value may leave the direction or size of an effect uncertain. A p-value addresses compatibility between observed data and a specified null model; it does not measure the probability that a treatment works, and it does not show whether an effect is clinically important. No primary-outcome confidence interval or p-value is reported in the registry record, so neither precision nor statistical evidence for a primary comparison can be assessed.

The registry’s sample-size assumptions describe planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The intended effect for an illustration is a stated fraction of the observed effect. These assumptions describe a calculation framework, not necessarily the trial’s original design. The registry record does not report the trial’s own sample-size justification, the effect used for each illustration, or a protocol-based power target. A planning illustration is not observed power and cannot establish what the completed trial was capable of detecting.

In general, over-dispersion matters when observed variation exceeds what a chosen probability model expects. A model that ignores over-dispersion can misstate uncertainty, often producing intervals or tests that are too optimistic. The primary endpoint is binary, and no dispersion parameter is identified for it in the registry record. A separate model-based treatment of over-dispersion therefore cannot be assessed or assumed from the information available.

The record lists several outcome measures, including local and systemic reactions, antibody response by hemagglutination inhibition assay, and a geometric mean ratio from Day 1 to Day 22. These outcomes answer different questions. Reaction counts describe reported safety events; antibody response and geometric mean ratio describe immunogenicity measures. In general, an immunogenicity measure is not interchangeable with a clinical disease outcome. The registry record does not provide the numerical results or enough detail about the assays, transformations, or analysis models to evaluate those outcomes statistically.

The analysis population also matters. The primary description names a safety set of vaccinated subjects with some post-baseline safety data, while the primary outcome title refers to randomized participants. The record does not further explain how these labels relate in the analysis, or how participants without post-baseline information were handled. In general, an analysis restricted to participants with observed follow-up can differ from an analysis retaining everyone as randomized, especially if missingness is related to treatment or outcome. The missing-data strategy is not reported in the registry record.

Finally, safety counts are descriptive unless accompanied by a prespecified comparative analysis and an account of uncertainty. The serious and other event counts can be read as numbers of affected participants within the stated groups, but they do not alone establish statistical differences. The record does not report whether the safety comparisons were adjusted for baseline factors, whether events were independently adjudicated, or whether multiple comparisons were addressed. Those omissions limit interpretation; they do not establish that such procedures were absent from the full study documentation.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcomes and several vaccine groups, including adult and elderly groups and elderly groups receiving influenza vaccine alone or with PV. Multiple outcomes and comparisons create a multiplicity issue: in general, the more hypotheses examined, the more opportunities there are for chance findings if each is tested without adjustment. The registry record does not report a multiplicity strategy, a hierarchy of confirmatory outcomes, or which comparisons were designated primary beyond naming the primary endpoint. It is therefore not possible to determine whether reported analyses were adjusted or how any secondary findings should be treated.

The primary outcome population is described as vaccinated subjects with some post-baseline safety data. The primary outcome title refers to randomized participants, but the record does not explain the relationship between that wording and the safety-set definition. It also does not report the number of participants with missing outcome information, reasons for missingness, or any imputation, censoring, or sensitivity-analysis method. In general, missing-data methods rely on assumptions about why data are absent; without the missingness pattern and analysis approach, the effect of missing information cannot be assessed.

Secondary outcomes distinguish randomized and unrandomized participants for reaction reporting and include antibody response and a geometric mean ratio. The registry record does not describe the specific analysis populations for all outcomes, the handling of participants who did not complete follow-up, or whether analyses followed randomized assignment. It also does not report interim analyses or the statistical plan. These details are not reported in the registry record and should not be inferred from the completed status or the recorded design.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: sinus bradycardia (2.0%), hypoacusis (2.0%), inner ear disorder (2.0%), tinnitus (2.0%), vertigo (2.0%).

The adverse-event figures are counts of affected participants among the stated group sizes. For example, the registry reports 17 serious-event participants among 550 in the cTIV adult group and 219 participants with other events among 550. The corresponding eTIV a adult figures are 5 among 168 for serious events and 73 among 168 for other events. The other six group counts are reported in the same form and are stated in the statistical interpretation.

These are descriptive safety figures. The registry record does not provide definitions of “serious” and “other” in the information available for this analysis, nor does it explain whether a participant could contribute to both categories. The figures should not be added together or treated as mutually exclusive categories without that information. They also do not give event timing, severity grades, duration, or causal attribution.

The serious-event terms listed in the record—sinus bradycardia, hypoacusis, inner ear disorder, tinnitus, vertigo, and glaucoma—are each reported as 2.0%. The associated denominators and counts are not reported in the registry record. The listed terms cannot therefore be interpreted as group-specific rates or as evidence of a difference between vaccines. No deaths are tabulated for the listed groups in the record’s adverse-event information.

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

The record supports a description of what the study set out to evaluate: safety, tolerability, and immunogenicity of cTIV and eTIV a, with an elderly subgroup evaluating concomitant pneumococcal vaccination. It also documents a randomized, single-blind, parallel-group Phase III extension study and gives group-level counts for serious and other adverse events. Those details can inform a careful account of the trial’s scope and the safety data that are registered.

The record does not report the numerical primary outcome of local and systemic reactions, despite defining its timeframe as one week after vaccination. It also does not include the numerical antibody-response results in the information available for this analysis. As a result, no estimate of the primary outcome’s comparative effect or its precision can be stated. The adverse-event counts do not fill that gap because they are not identified as the primary local and systemic reaction outcome.

In general, a nonsignificant result would not prove that two groups are equivalent, and a statistically significant result would not by itself establish clinical importance. Such interpretations require an analysis estimate, uncertainty interval, outcome definitions, and a suitable comparison plan. Those results and details are not reported in the registry record. Similarly, the absence of a reported event in a group should not be interpreted as proof that the event cannot occur.

The study’s extension context also defines the population to which its findings might apply: adults and elderly subjects who had participated in Study V58P4, with a specific elderly subgroup for concomitant vaccination. The record does not establish how representative these participants were of people outside that setting. Accordingly, the registry supports a description of the study design and recorded event counts, but not a broad conclusion about comparative vaccine effects or the incidence of events beyond the enrolled groups.

13. Why This Trial Matters Statistically

This trial raises several statistical questions that are useful in reading vaccine studies. First, it distinguishes safety outcomes from immunogenicity outcomes. Counting reported reactions and assessing antibody response are different measurement tasks, and they require different interpretations. A reaction count does not tell the reader what antibody response occurred, while an antibody measure does not by itself describe the frequency of reported reactions.

Second, the design contains more than one relevant comparison context. The registry includes cTIV and eTIV a groups, adults and elderly participants, and an elderly subgroup in which PV was administered concomitantly. Such structure makes clear why group labels and analysis populations matter: results should be interpreted against the specific participants and treatment setting that produced them, not generalized across all groups without evidence.

Third, the primary endpoint is described as a participant count during a defined period after vaccination, while the posted adverse-event figures are organized as serious and other events. Keeping these categories distinct is statistically important. A well-defined endpoint, denominator, and follow-up period are needed before estimates can be compared meaningfully. The registry record gives a timeframe for the primary endpoint but does not provide its numerical group results or enough detail to reconcile it with the adverse-event counts.

Finally, this record illustrates that trial registration and results reporting answer different questions. Design information can identify the intended population, interventions, and outcomes; numerical results and analysis details are needed to evaluate effect size and uncertainty. Here, several important analysis details are not reported in the registry record. Recognizing those gaps is part of interpreting evidence carefully rather than treating a completed trial or a set of event counts as a complete statistical conclusion.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation is that numerical results for the named primary endpoint are not reported in the registry record. The group-level serious and other adverse-event counts are available, but the record does not establish that these correspond to the primary measure of local and systemic reactions within one week. They should not be substituted for missing primary-endpoint data.

The adverse-event information lacks detail needed for a fuller interpretation. Definitions and grading criteria, event timing, causal assessment, and the relationship between serious and other categories are not reported in the registry record. The serious-event terms are listed at 2.0% each, without corresponding denominators or counts in the information available for this analysis. These data cannot support detailed group comparisons of those terms.

The trial population is described as adults and elderly subjects who participated in Study V58P4, and the registry reports an elderly subgroup for concomitant PV. Further eligibility details, participant characteristics, and the relationship between the extension population and the earlier study are not reported in the registry record. The generalizability of the group counts therefore cannot be evaluated from the available information.

Important methods are also not reported, including the randomization procedure, allocation ratio, identity of the masked party, missing-data handling, multiplicity strategy, and full statistical analysis plan. The registry record does not provide numerical immunogenicity results or uncertainty intervals for the primary comparison. These limitations restrict assessment of bias, precision, and comparative effects; they do not show that the full study documentation lacked such details.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Second Extension Study to Evaluate Safety and Tolerability of Influenza Vaccines in Adults and Elderly, and to Evaluate Immunogenicity and Concomitant Vaccination With Pneumococcal Vaccine in a Subgroup — NCT00579345.
• Registry record last updated 2017-01-27; status last verified 2012-10.
• Results first posted 2011-10-10.
• 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

This completed Phase III extension study enrolled 1522 adults and elderly subjects who had participated in Study V58P4. It was randomized, single-blind, parallel-group, and multicenter. The study evaluated cTIV and eTIV a, including concomitant administration with PV in an elderly subgroup. The primary outcome concerned local and systemic reactions within one week after vaccination.

The registry reports counts of participants with serious and other adverse events across eight groups. It does not report numerical results for the primary endpoint or the listed immunogenicity outcomes in the information available for this analysis. Several analysis details, including missing-data and multiplicity methods, are also not reported in the registry record. The registered design and safety counts can be described, but they do not provide a complete comparative statistical assessment.