Safety and Immunogenicity Study of 20vPnC When Coadministered With a Booster Dose of BNT162b2: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Immunogenicity Study of 20vPnC When Coadministered With a Booster Dose of BNT162b2 (NCT04887948), a randomized phase 3 study. The primary outcome is Percentage of Participants With Local Reactions at Each Injection Site Within 10 Days After Vaccination.

2. Clinical Question

3. Trial Design

This was a randomized, triple-masked, parallel phase 3 trial sponsored by Pfizer. The registry lists enrollment as 570 and the study status as completed. The recorded start date is 2021-05-20, and the primary completion date is 2021-12-08. The study concerned pneumococcal disease, COVID-19, and SARS-CoV-2 infection, and assessed the safety and immunogenicity of 20vPnC when given with a booster dose of BNT162b2 in adults 65 years of age and older.

Participants were assigned to one of three groups. The coadministration group received 20vPnC and BNT162b2 at the same visit. The 20vPnC-only group received 20vPnC and saline, while the BNT162b2-only group received BNT162b2 and saline. The registry identifies the allocation as randomized, masking as triple, and model as parallel. It does not report the allocation ratio, the precise identities of the masked parties, any stratification variables, or details of the randomization procedure.

The primary outcome assessed local reactions at each injection site within 10 days after vaccination. Other listed outcomes concern pneumococcal serotype-specific opsonophagocytic activity and full-length S-binding immunoglobulin G after vaccination. The registry lists 7 outcome measures and 0 analyses. The protocol’s detailed statistical analysis plan, including which comparisons were intended to support formal inference, is not reported in the registry record. The enrollment figure is a study-level record and should not be treated as the number analyzed for a particular endpoint. The endpoint-specific analysis population is described in the outcome definition, but the primary endpoint’s analyzed counts and results are not reported.

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 570 participants were enrolled in the study and randomized to a study treatment.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety population included all participants who received at least 1 dose of the study intervention and had safety follow-up after vaccination. Here, "Overall Number of Participants Analyzed" signifies number of participants with any e-diary data reported after vaccination.

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: Safety population included all participants who received at least 1 dose of the study intervention and had safety follow-up after vaccination.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Local Reactions at Each Injection Site Within 10 Days After Vaccination, measured over Within 10 days after vaccination.

The primary endpoint is the percentage of participants with local reactions at each injection site within 10 days after vaccination. The recorded reactions were pain at the injection site, redness, and swelling, captured by participants in an electronic diary. Redness and swelling were measured using a measuring device; the registry states that 1 measuring device unit equals 0.5 centimeter. It describes severity grades for redness and swelling as mild, moderate, and severe, and grades pain according to whether it interfered with or prevented daily activity.

This endpoint is used to describe short-term, injection-site tolerability after vaccination. Reporting by injection site matters because the coadministration group received two vaccines at the same visit, while the comparison groups received one active vaccine and saline. The endpoint’s definition therefore calls for attention to the site as well as the group and follow-up period. It is not a measure of immune response or of protection against disease.

The registry says the percentage and an associated 2-sided 95% confidence interval were to be presented using the Clopper and Pearson method. However, the primary outcome has several categories or time points and is not reduced to one comparison in the available analysis. Numerical percentages, confidence limits, and endpoint-specific analyzed counts are not reported in the registry record. Consequently, the endpoint definition can be described, but the frequency and precision of the recorded reactions cannot be assessed from the registry entries available.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical explanation: A percentage summarizes how common an event was in the analyzed group. A confidence interval expresses uncertainty around an estimated percentage: it gives a range of values that are compatible with the data under the method’s assumptions. A narrow interval generally indicates greater precision than a wide one, but the registry record does not report the primary endpoint’s percentages or intervals, so the precision of those results cannot be evaluated.

What does the endpoint-specific interval represent?

The registry names the Clopper and Pearson method for the 2-sided 95% confidence interval around the percentage of participants with local reactions. In general, this is an exact binomial interval for a proportion, constructed from the event count and the number analyzed. “Exact” describes the method used to obtain the interval; it does not mean that the interval removes uncertainty or that it accounts for every possible source of bias. The endpoint description does not include the event counts or analyzed denominators needed to reproduce or inspect the reported estimates. Those primary-outcome values are not reported in the registry record.

The unit of interpretation also matters. The endpoint concerns participants with reactions at each injection site, within the stated 10-day period. A participant may contribute information about more than one reaction type or site, depending on the endpoint’s specific categories. The registry record does not provide enough outcome-level detail to determine how such observations were combined or whether any within-participant dependence was addressed in a formal model. It would therefore be inappropriate to infer a more elaborate analysis from the endpoint wording alone.

Why distinguish description from comparison?

General statistical explanation: Group-specific estimates describe what was observed in each group. A formal comparison evaluates uncertainty in a difference or another contrast between groups. Looking at group counts alone is not the same as testing a contrast, and a numerical difference in observed counts does not by itself establish a reliable treatment-related difference. A comparison also depends on its specified estimand, analysis population, method, and handling of missing observations. The registry record does not report a single primary contrast or its uncertainty for the local-reaction endpoint.

Randomization can support a fair comparison when the planned analysis preserves the randomized groups and follows the trial’s stated methods. But randomization does not make all design and analysis details unnecessary. The allocation ratio and randomization procedure are not reported in the registry record, and neither are the endpoint results needed to assess group balance or comparative precision. Masking is identified as triple, but the record does not name which parties were masked. No further interpretation of masking procedures is warranted from that label alone.

What does over-dispersion mean in general?

General statistical explanation: For count outcomes, a simple model may assume that the variation is described by a particular probability distribution. Over-dispersion occurs when the observed variation is greater than that assumption allows. If it is ignored, standard errors can be too small and confidence intervals too narrow. This concept is relevant when a count-based analysis uses a model that makes a restrictive variance assumption. The registry’s primary endpoint is a percentage, and no over-dispersion model or count-model analysis is reported. It would not be appropriate to claim that over-dispersion affected this trial’s results.

The named Clopper and Pearson method addresses uncertainty in a proportion under a binomial framework; it does not, by itself, resolve questions about missing diary entries, repeated measurements, multiplicity, or the choice of comparison. The registry defines the primary endpoint population as participants with any electronic-diary data after vaccination, but does not report how partially completed diaries were handled. The analysis details for repeated reaction categories or sites are not reported in the registry record.

How should planning calculations be read?

General statistical explanation: A sample-size calculation illustrates how much information a future study might need under stated assumptions. The registry’s planning description uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It specifies detecting a stated fraction of the observed effect. For outcomes other than time-to-event outcomes, the illustration is expressed as participants per arm for 80% or 90% power; time-to-event illustrations use the total number of events under the Schoenfeld method. These are planning illustrations, not observed power and not a retrospective measure of whether the completed trial was adequate.

The registry record does not report the numerical planning values, the observed effect used for the illustration, or the trial’s own sample-size justification. It also does not report whether interim analyses were planned or conducted. Those details cannot be reconstructed from the stated assumptions. Any planning output should be interpreted only in relation to the assumptions attached to it, and not as an observed clinical finding or a substitute for the missing outcome estimates.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 7 outcome measures, including the primary local-reaction outcome and secondary immune-response outcomes. Considering several outcomes, reaction types, time points, or group comparisons can create a multiplicity issue: when many statistical tests are conducted, the chance of at least one apparently unusual result may increase. General statistical explanation: multiplicity procedures can control or describe this issue, but the appropriate approach depends on which outcomes and comparisons are confirmatory and how they were prespecified. The registry does not report a multiplicity adjustment, a testing hierarchy, or a complete statistical analysis plan. It is therefore not possible to determine from the registry record how multiplicity was handled.

The primary outcome has several categories or time points and is not reduced to one comparison. This means the record does not identify one summary estimate that can stand in for every local reaction, injection site, and time point. The primary outcome’s category-specific results and inferential comparisons are not reported in the registry record. The listed immune-response outcomes likewise do not include numerical results in the record.

The primary endpoint population includes participants with any electronic-diary data reported after vaccination. That definition clarifies who could contribute to the endpoint, but does not explain how missing diary days, incomplete entries, or missing measurements were handled. The amount and pattern of missing endpoint data, any imputation approach, and any sensitivity analyses are not reported in the registry record. Missing-data methods can affect estimates if the likelihood of missingness is related to reactions or group assignment, so the analyzed denominator and handling strategy are important to interpretation.

The safety population is defined as participants who received at least 1 dose and had safety follow-up after vaccination. The primary endpoint’s analyzed population has an additional diary-data condition. These definitions should not be treated as interchangeable. The record does not provide all endpoint-specific analysis counts, nor does it state whether the immune-response analyses used the same population. The registry lists 0 analyses; this does not establish that no analyses were performed, only that analyses are not listed in that registry field. Details about analysis populations and missingness beyond the stated definitions are not reported in the registry record.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: femur fracture (0.5%), breast cancer stage i (0.5%), lung adenocarcinoma (0.5%), metastases to liver (0.5%), small intestine carcinoma (0.5%).

The registry reports serious adverse event counts alongside the numbers at risk in each group. The coadministration group has 1 serious adverse event among 187 at risk; the 20vPnC-only group has 2 among 187; and the BNT162b2-only group has 5 among 185. The recorded deaths are 1 in the coadministration group and 0 in each of the other groups. Other adverse event counts are 157 among 187, 137 among 187, and 149 among 185, respectively. These figures describe recorded counts and denominators; they are not percentages or adjusted comparisons.

The registry also lists serious-event terms, each with a recorded frequency of 0.5%: Femur fracture, Breast cancer stage I, Lung adenocarcinoma, Metastases to liver, Small intestine carcinoma, and Acute kidney injury. The record does not map these terms to specific groups in the information, so no group assignment should be inferred. A serious adverse event is not necessarily an event caused by the study intervention. The counts do not establish causality, and the registry record does not report comparative confidence intervals or tests for these safety outcomes.

For a fuller safety interpretation, readers would need the event definitions, follow-up period, completeness of ascertainment, and prespecified analysis methods. Those details are not all reported in the registry record. The counts are best read as descriptive safety information rather than definitive evidence of a difference among groups.

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

The trial was designed to describe safety and immunogenicity when 20vPnC and a booster dose of BNT162b2 were administered at the same visit or separately. Its randomized, parallel design and three treatment groups define a framework for comparing the regimens. The primary endpoint focuses on short-term local reactions, while the secondary outcomes address immune responses. These design features explain what the trial set out to examine, but they are not themselves evidence of a particular result.

The primary endpoint’s definition is available, and the registry includes selected adverse-event counts. However, the numerical local-reaction percentages and confidence intervals are not reported in the registry record. Nor are numerical results for the listed immune-response outcomes. Without those estimates, it is not possible to judge the observed frequency of local reactions, the precision of the estimates, or the magnitude and uncertainty of any group contrast. The absence of these results should not be interpreted as a finding of no difference.

The safety counts can inform a descriptive account of events recorded in the three groups, but they do not independently establish whether an event was caused by vaccination. They also do not constitute a formal comparison. The registry does not report the statistical tests or confidence intervals for these counts. No assertion about relative safety or immune response follows from the counts alone.

General statistical explanation: Statistical evidence is most useful when an estimate is considered together with its uncertainty, the analysis population, and the design of the comparison. A confidence interval can indicate the range of values compatible with a result under the specified method, while a test addresses a particular hypothesis under its assumptions. Neither can answer every question about clinical importance or causality. In this record, essential numerical primary and immune-response estimates are missing, and key analysis details are not reported.

Accordingly, the record supports conclusions about the study’s stated design, intervention groups, endpoint definitions, and selected descriptive safety counts. It does not support a complete quantitative assessment of the primary endpoint or immunogenicity, nor a definitive comparative conclusion across regimens. Those distinctions are important when interpreting any reported counts alongside the endpoint descriptions.

13. Why This Trial Matters Statistically

This trial raises a useful statistical question because it compares coadministration with each vaccine given alongside saline. The three-arm design makes the intended contrasts interpretable in principle: the combined regimen can be considered alongside 20vPnC alone and BNT162b2 alone. Randomization is a design feature intended to support group comparisons, while masking can reduce certain forms of bias. The registry identifies the study as randomized, triple-masked, and parallel, but does not report enough procedural detail to assess all aspects of those protections.

The local-reaction endpoint also illustrates why outcome definitions matter. Reactions are tied to injection site, type, severity, and a defined period after vaccination. A single percentage cannot necessarily represent every category or time point. The registry explicitly notes that the primary outcome has several categories or time points and is not reduced to one comparison. That makes it important to know which contrasts were prespecified and how multiplicity was handled; those analysis details are not reported in the registry record.

Precision is another central issue. The endpoint description names a confidence-interval method, but the numerical estimates and intervals are absent from the registry record. Without them, readers cannot evaluate how precise the local-reaction estimates were. Similarly, the immune-response outcomes are described but their values are not reported. This distinction between a measured outcome and an available result is fundamental to statistical interpretation.

The study is also a reminder that adverse-event counts need context. Counts and denominators provide descriptive information, but they do not show causal attribution or uncertainty around between-group differences. For complete interpretation, a reader needs the analysis population, follow-up and missing-data details, and any planned inferential methods. The registry offers some population definitions and safety counts, while leaving important analysis information unreported.

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.

Several limitations arise from what is and is not recorded. The primary outcome is described as having multiple categories or time points, and the registry does not reduce it to a single comparison. Numerical local-reaction results, analyzed denominators, confidence intervals, and a named primary contrast are not reported in the registry record. As a result, the central safety endpoint cannot be quantitatively interpreted from the record alone.

The registry lists secondary immune-response outcomes but does not report their numerical results. Consequently, the record does not permit an assessment of pneumococcal serotype-specific opsonophagocytic activity or of the stated S-binding IgG measures. It also does not report a complete statistical analysis plan, multiplicity strategy, interim-analysis information, or the trial’s sample-size justification. These absences prevent reconstruction of the intended inferential framework.

Population definitions are available, but the handling of incomplete electronic diaries and other missing outcome data is not. The record does not give endpoint-specific analysis counts for the primary results. It therefore remains unclear how much diary information was available and how missing entries affected the planned estimates. The safety counts are descriptive, without reported uncertainty intervals or statistical comparisons in the record.

Finally, the available information does not identify which parties were masked, detail the randomization process, or provide enough follow-up and event-ascertainment information to evaluate all safety outcomes. These details should not be inferred from the trial’s design labels. The limitations do not show that the study was improperly conducted; they describe what cannot be assessed from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Safety and Immunogenicity Study of 20vPnC When Coadministered With a Booster Dose of BNT162b2 — NCT04887948.
• Registry record last updated 2022-12-14; status last verified 2022-11.
• Results first posted 2022-12-14.
• 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

NCT04887948 is a completed, randomized, triple-masked, parallel phase 3 study sponsored by Pfizer. It enrolled 570 adults 65 years of age and older and compared 20vPnC plus BNT162b2 at the same visit with 20vPnC plus saline and BNT162b2 plus saline. The primary endpoint was the percentage with local reactions at each injection site within 10 days after vaccination, with a 2-sided 95% confidence interval specified using the Clopper and Pearson method.

The registry record lists selected serious and other adverse-event counts, as well as secondary immune-response outcomes. It does not report numerical primary-endpoint results, numerical immune-response results, a single primary comparison, or a complete statistical analysis plan. The safety counts should therefore be treated as descriptive rather than as causal or formal comparative evidence.