Immunization To Prevent Acute COPD Exacerbations: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Immunization To Prevent Acute COPD Exacerbations (NCT03276754), a registered phase not stated study. The primary outcome is Change in Adjusted Rate of Moderate/Severe COPD Exacerbations at Month 24 in PCV 13 Population.

2. Clinical Question

The endpoint focused on exacerbations requiring a change in treatment, distinguishing moderate events from severe events that led to hospitalization. The study also listed outcomes involving influenza vaccination history, respiratory health questionnaires, lung function, and PCV13 vaccination. Their presence as planned outcomes does not establish what was observed: the registry record lists no outcome analyses.

3. Trial Design

The registry describes a prospective, multicenter observational study of routine clinical practice vaccination with PCV13. Its stated purpose was to evaluate the impact of vaccination on the risk of moderate or severe COPD exacerbations. Because the design is observational, the record does not describe vaccination as randomly assigned. Allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison.

The study began on 2017-11-30, had a primary completion date of 2022-06-16, and is listed as terminated. The registry records enrollment of 530 participants. The reason for termination is not reported in the registry record. A planned or actual follow-up schedule beyond the primary endpoint's Baseline and Month 24 timeframe is not reported in the registry record.

The primary endpoint is the change in adjusted rate of moderate or severe COPD exacerbations at Month 24 in the PCV13 population. The endpoint description defines the adjusted rate using the total number of moderate or severe exacerbations and participant follow-up time, scaled to 24 months. The population definition specifies evaluable participants vaccinated with PCV13 at least 1 month before informed consent and not subsequently vaccinated with PPSV23.

The registry lists 8 outcome measures, including the primary exacerbation measure and secondary measures related to influenza vaccination history, Saint George Respiratory Questionnaire scores, COPD Assessment Test scores, forced expiratory volume, and PCV13 vaccination. It lists 0 analyses. A detailed protocol, allocation procedure, comparator definition, and reason for termination are not reported in the registry record. The observational design and absence of a stated allocation procedure limit how directly any between-group differences could be interpreted as effects of vaccination.

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: A total of 530 evaluable participants were included in the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: PCV13 population included evaluable participants who were administered PCV13 at least 1 month prior providing informed consent to participate in the study and who did not subsequently received PPSV23. All participants reported under "Overall Number of Participants Analyzed" contributed data to the table; however, may not have evaluable data for every row.

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: Analysis population included all evaluable participants whose data were included and prospectively observed in the study.

6. Primary Endpoint

The registry lists the primary outcome as Change in Adjusted Rate of Moderate/Severe COPD Exacerbations at Month 24 in PCV 13 Population, measured over Baseline and Month 24.

The primary endpoint is the change in adjusted rate of moderate or severe COPD exacerbations at Month 24 in the PCV13 population. The unit is exacerbations per participant in 24 months, and the endpoint is described as a mean with standard deviation. Its calculation uses the total number of moderate or severe exacerbations divided by participant follow-up time in months, then scaled to 24 months. No numerical endpoint estimate or standard deviation is reported in the registry record.

An exacerbation was defined as a complex of at least two respiratory symptoms related to underlying COPD, lasting 3 days or more and requiring a change in treatment. Symptoms included worsening dyspnea, cough, sputum production, chest tightness, or wheezing. Moderate exacerbations required antibiotics and/or systemic corticosteroids without hospitalization; severe exacerbations led to hospitalization.

General statistical context: expressing an event rate relative to follow-up time can account for participants contributing different amounts of observation. Scaling a rate to a stated period makes its time basis explicit. The adjusted rate is the endpoint named in the registry, but the adjustment variables and model are not reported in the registry record. The endpoint is clinically interpretable as an event-frequency measure, but without a posted estimate and uncertainty interval, its magnitude and precision cannot be assessed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is described as a mean of a continuous measure, with standard deviation as its dispersion measure. In general, a mean represents the arithmetic center of observed values, while a standard deviation describes how spread out those values are around the mean. The registry record gives neither the mean nor the standard deviation for the primary outcome, so the observed distribution and the precision of its estimate cannot be evaluated from the posted outcome information.

What does an adjusted rate represent?

The registry defines the adjusted rate as the total number of moderate or severe exacerbations divided by participant follow-up time in months, multiplied by 24 months. This puts the event rate on a common time scale, which can be useful when participants have differing observation time. It is a rate measure, not a count of participants affected and not a measure of time until a first event. No numerical rate is reported in the registry record. The meaning of “adjusted” beyond the stated formula is not detailed: the adjustment model, variables, and estimation method are not reported in the registry record.

Why can event rates vary more than a simple model expects?

General statistical context: count outcomes are sometimes analyzed with models that assume the variability in event counts follows a particular relationship to the average count. Over-dispersion means the observed variability is greater than that assumption allows. If present and not accounted for, uncertainty estimates can be too narrow, making results appear more precise than warranted. This is a general consideration for recurrent event data, not a claim that over-dispersion occurred in this study. The registry record does not report a model, a dispersion assessment, or a method for handling recurrent events.

What do standard deviations and confidence intervals convey?

General statistical context: a standard deviation describes variation among observed measurements, whereas a confidence interval describes uncertainty around an estimated quantity under the assumptions of the analysis. They answer different questions. A confidence interval can help readers assess which values remain compatible with the data and model, but it does not remove design limitations or establish causation. No standard deviation or confidence interval for the primary endpoint is reported in the registry record. No p-value for the endpoint is reported either.

How should the observational design shape interpretation?

The registry identifies the study as prospective, multicenter, and observational. It does not state an allocation procedure and specifically notes that the comparison is not randomized and the arms are not a like-for-like control comparison. General statistical context: random allocation can help balance both measured and unmeasured characteristics on average, while observational comparisons do not gain that protection from design. Adjustment may address measured variables if they are appropriately selected and modeled, but it cannot automatically resolve unmeasured confounding. The registry does not report enough information to judge which variables were considered or how adjustment was performed.

What can the planning assumptions tell readers?

The sample-size planning illustration is described as using the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that the study had a particular probability of detecting an effect. The registry record does not report the trial's own sample-size justification. No numerical planning requirements are stated in the available record details. The calculation assumptions also do not resolve the lack of a randomized, like-for-like comparison or substitute for a reported outcome estimate.

For time-to-event planning illustrations, the stated convention is to report the total number of events using the Schoenfeld method; other illustrations report participants per arm. General statistical context: planning quantities depend on assumptions about the target effect and design, and should not be confused with the sample actually enrolled or analyzed. Here, enrollment was 530, but the number included in the primary endpoint analysis is not reported in the registry record. No interim analyses, detailed statistical analysis plan, or missing-data method is reported in the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Participants With COPD")
n   <- c(114)
m   <- c(-1.1)
sp  <- c(2.5)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Participants With COPD  114  -1.100  2.500  -1.564  -0.636

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 8 outcome measures, including the primary exacerbation endpoint and secondary outcomes concerning influenza vaccination history, respiratory health questionnaire scores, COPD assessment scores, forced expiratory volume, and PCV13 vaccination. It lists 0 analyses. Although outcomes are named, numerical findings and analysis details are not reported in the registry record.

General statistical context: when a study evaluates multiple outcomes or makes multiple comparisons, the chance of at least one apparently unusual result can increase if each result is interpreted without considering the full set of analyses. A prespecified multiplicity strategy can help define how evidence is assessed across outcomes. The registry record does not report a multiplicity adjustment, a hierarchy among the outcomes, or which analyses were prespecified. No adjustment method should be inferred from the outcome list alone.

Missing-data handling is also not reported in the registry record. The record does not say how missing endpoint observations, incomplete follow-up, or participants without evaluable data were treated. General statistical context: missingness can affect an estimate when the chance of having a recorded outcome is related to participant characteristics or outcome status. Different methods rely on different assumptions, so the method and supporting information matter for interpretation.

The primary population is described by PCV13 vaccination timing and subsequent PPSV23 status, but its analyzed size is not reported in the registry record. The stated overall enrollment of 530 should not be substituted for the size of that endpoint population. The available population description is incomplete, and additional analysis-population definitions are not reported in the registry record. An interim-analysis plan, stopping rules, and the detailed statistical analysis plan are not reported in the registry record.

12. 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 (3.2%), covid-19 pneumonia (1.9%), death (1.7%), chronic obstructive pulmonary disease (1.3%), cardio-respiratory arrest (1.1%).

For participants with COPD, the registry lists 530 participants at risk for serious adverse events and 78 participants with serious adverse events. It lists 530 at risk for other adverse events and 10 participants with other adverse events. The record also lists 39 deaths. These are descriptive counts in the registry record; they do not establish why an event occurred or whether it was caused by vaccination or another factor.

The listed serious-event terms and percentages are pneumonia, 3.2%; COVID-19 pneumonia, 1.9%; death, 1.7%; chronic obstructive pulmonary disease, 1.3%; cardio-respiratory arrest, 1.1%; and cardiac failure, 0.8%. These are registry-listed event categories and should not be treated as a causal attribution. The record does not provide additional context about timing, individual event histories, or how events were judged related to vaccination.

General statistical context: safety counts describe events recorded during observation, while causal interpretation requires information about exposure timing, comparison groups, follow-up, and alternative explanations. Because this was observational and the registry cautions that the arms are not a like-for-like control comparison, the adverse-event figures alone cannot estimate a causal risk difference. The reason for termination and further safety-analysis details are not reported in the registry record.

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

The registry record describes an observational study designed to evaluate routine clinical practice PCV13 vaccination in relation to moderate or severe COPD exacerbations. It defines the primary endpoint as a change in adjusted exacerbation rate at Month 24 in a specifically defined PCV13 population. It also records enrollment of 530 participants and lists secondary outcome topics and safety counts.

Those design details do not supply the primary result. The registry lists 0 analyses and does not report a numerical estimate, uncertainty interval, or p-value for the primary endpoint. It is therefore not possible to quantify the observed change, judge its precision, or determine what the posted data indicate about a comparison. No conclusion about treatment benefit or lack of benefit follows from the absence of a posted estimate.

The endpoint population is defined by vaccination timing and later PPSV23 status, and may not correspond to all enrolled participants. The number meeting that definition is not reported in the registry record. The record also does not state the comparator definition, allocation procedure, adjustment variables, missing-data methods, or reason for termination. These gaps limit assessment of how the endpoint would be estimated and how comparable any groups were.

General statistical context: an observational estimate can describe an association, but design and analysis details are needed to assess alternative explanations and uncertainty. Even a precise estimate would not, by itself, remove possible confounding or turn a nonrandomized comparison into a randomized one. In this case, the posted registry information does not provide a numerical estimate to evaluate in the first place.

The safety figures are counts of participants and listed event terms, not proof of causation. They should be read as descriptive registry information, alongside the study's observational design and the absence of detailed event context. The registry record is informative about the study question, endpoint definitions, listed outcomes, and reported safety counts, but it does not provide enough outcome-analysis information to determine the magnitude or precision of the primary finding.

14. Why This Trial Matters Statistically

This study raises a statistical question that depends on both outcome definition and study design. COPD exacerbations are defined using symptoms, duration, and treatment change, with moderate and severe events distinguished by hospitalization status. The endpoint is a rate scaled to 24 months, so it concerns recurrent event frequency relative to follow-up rather than simply whether a participant experienced an event.

The prospective, multicenter observational design is important for interpretation. Vaccination occurred in routine clinical practice, and the registry does not state an allocation procedure. It explicitly cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. This makes the comparator definition and adjustment details especially relevant. Those details are not reported in the registry record.

The record also illustrates why an endpoint description is not a substitute for a result. Although the primary measure, population criteria, and several secondary outcomes are named, the record lists 0 analyses and supplies no numerical primary estimate or uncertainty interval. Without those quantities, readers cannot assess the observed magnitude or precision. The number enrolled, 530, likewise does not reveal how many participants contributed to the endpoint analysis.

Finally, recurrent events, follow-up time, and the use of an adjusted rate call for clear analytical reporting. The registry describes the rate formula but does not report the adjustment model, dispersion handling, missing-data approach, or multiplicity strategy. General statistical context: documenting these choices helps readers understand which assumptions connect the observed records to an estimated outcome. The absence of a reported result and analysis detail means that the statistical question remains identifiable, but the evidence needed to evaluate its answer is not reported in the registry record.

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.

Important trial-specific limitations arise from the information recorded about design and analysis. The study is observational, allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison. The comparator definition is not reported in the registry record. These features constrain interpretation of any between-group contrast and prevent a causal conclusion based on design alone.

The primary endpoint is defined, but its numerical result, standard deviation, confidence interval, and p-value are not reported in the registry record. The registry lists 0 analyses. The adjustment variables and model are not reported, so the meaning of the adjusted estimate cannot be evaluated beyond the rate formula. The number of participants in the defined PCV13 endpoint population is also not reported, despite enrollment of 530.

The population description specifies receipt of PCV13 at least 1 month before informed consent and no subsequent PPSV23, but the available endpoint wording does not provide a complete account of the analysis population. Further eligibility and analysis details are not reported in the registry record. The registry also does not report missing-data handling, interim analyses, a multiplicity strategy, or a detailed statistical analysis plan.

The status is terminated, but the reason is not reported in the registry record. The record does not establish whether the planned follow-up was completed or explain the status. Safety counts and listed event percentages lack additional information about timing or attribution, so they cannot establish causation. Together, these limitations leave the study question and endpoint clear while leaving the primary statistical result and several key interpretation details unavailable.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Immunization To Prevent Acute COPD Exacerbations — NCT03276754.
• Registry record last updated 2024-08-19; status last verified 2024-08.
• Results first posted 2024-08-19.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry identifies NCT03276754 as a prospective, multicenter observational study of routine clinical practice PCV13 vaccination in people with COPD. Enrollment was 530. The study began on 2017-11-30, had a primary completion date of 2022-06-16, and is listed as terminated.

The primary endpoint concerns the adjusted rate of moderate or severe COPD exacerbations at Month 24 in the PCV13 population. The registry lists 8 outcome measures and 0 analyses. A numerical primary result, analysis details, comparator definition, and reason for termination are not reported in the registry record.

The safety record lists 78 participants with serious adverse events, 10 with other adverse events, and 39 deaths among the 530 participants with COPD. These figures are descriptive and do not establish causation. The record identifies the study question and outcome definitions, but does not report the numerical primary endpoint result or its precision.