Solicited ARs (local and systemic) were reported by participants an electronic diary (eDiary). Local ARs included: injection site pain, injection site erythema (redness), injection site swelling/induration (hardness), and axillary (underarm) swelling or tenderness ipsilateral to the side of injection. Systemic ARs included: fever, headache, fatigue, myalgia, arthralgia, nausea/vomiting, and chills.

The solicited safety set included all randomized participants who receive the study intervention and contribute any solicited AR data. Participants were included in the vaccination group corresponding to what they actually received (as treated).

An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. Any abnormal laboratory test result (hematology, clinical chemistry, or prothrombin time [PT]/partial thromboplastin time [PTT]) or other safety assessment (for example, electrocardiogram, radiological scan, vital sign measurement), including one that worsened from baseline and was considered clinically significant in the medical and scientific judgment of the Investigator was recorded as an AE. Severity for all unsolicited AEs was determined by the Investigator based upon medical judgment and graded as Mild, Moderate or Severe. Number of participants with unsolicited AEs (SAEs and non-serious AEs) and severe AEs up to 28 days post-vaccination are reported in this outcome measure. A Summary of serious AEs (SAEs) and nonserious AEs ("Other"), regardless of causality, is located in the "Reported Adverse Events" section.

The Safety Set included all randomized participants who received the study intervention. Participants were included in the vaccination group corresponding to what they actually received (as treated).

An SAE was defined as any AE that resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in disability/permanent damage, was a congenital anomaly/birth defect, or was an important medical event. AESIs were protocol-defined medical concepts. An MAAE is an AE that lead to an unscheduled visit to an healthcare practitioner. This included visits to a study site for unscheduled assessments (for example, abnormal laboratory follow-up, and/or COVID-19 and visits to healthcare practitioners external to the study site. Number of participants with SAEs, AESIs, MAAEs, and AEs leading to study discontinuation up to Day 181 are reported in this outcome measure. A Summary of serious AEs (SAEs) and nonserious AEs ("Other"), regardless of causality, is located in the "Reported Adverse Events" section.

The Safety Set included all randomized participants who received the study intervention. Participants were included in the vaccination group corresponding to what they actually received (as treated).

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Antibody values reported as below the lower limit of quantification (LLOQ) were replaced by 0.5 * LLOQ. Values greater than the upper limit of quantification (ULOQ) were converted to the ULOQ. LLOQ = 10 and ULOQ = 3620 for Influenza A H1N1 antibody, LLOQ = 10 and ULOQ = 5120 for Influenza A H3N2 antibody, LLOQ = 10 and ULOQ = 1356 for Influenza B/Victoria-lineage antibody, and LLOQ = 10 and ULOQ = 1280 for Influenza B/Yamagata-lineage antibody. 95% confidence interval (CI) was calculated based on the t-distribution of the log-transformed values for geometric mean (GM) titer, then back transformed to the original scale for presentation. Arms based on the applicable vaccine for this Outcome Measure.

PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

SARS-CoV-2 strain included Omicron XBB.1.5 antibody. Antibody values reported as below the LLOQ are replaced by 0.5 * LLOQ. Values greater than the ULOQ are converted to the ULOQ. LLOQ = 38 and ULOQ = 6960 arbitrary units (AU)/milliliter (mL) for SARS-CoV-2 Omicron XBB.1.5 antibody. 95% CI was calculated based on the t-distribution of the log-transformed values for GM concentration, then back transformed to the original scale for presentation. Arms based on the applicable vaccine for this Outcome Measure.

PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values greater than the ULOQ were converted to the ULOQ. LLOQ = 10 and ULOQ = 3620 for Influenza A H1N1 antibody, LLOQ = 10 and ULOQ = 5120 for Influenza A H3N2 antibody, LLOQ = 10 and ULOQ = 1356 for Influenza B/Victoria-lineage antibody, and LLOQ = 10 and ULOQ = 1280 for Influenza B/Yamagata-lineage antibody. 95% CI was calculated based on the t-distribution of the log-transformed values for GMFR values, then back transformed to the original scale for presentation. Arms based on the applicable vaccine for this Outcome Measure.

PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

SARS-CoV-2 strain included Omicron XBB.1.5 antibody. Antibody values reported as below the LLOQ are replaced by 0.5 * LLOQ. Values greater than the ULOQ are converted to the ULOQ. LLOQ = 38 and ULOQ = 6960 AU/mL for SARS-CoV-2 Omicron XBB.1.5 antibody. 95% CI was calculated based on the t-distribution of the log-transformed values for GMFR values, then back transformed to the original scale for presentation. Arms based on the applicable vaccine for this Outcome Measure.

PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Seroconversion was defined as a pre-vaccination HAI titer <1:10 and a post-vaccination HAI titer ≥1:40 or a pre-vaccination HAI titer ≥1:10 and a minimum 4-fold rise in post-vaccination HAI antibody titer. Arms based on the applicable vaccine for this Outcome Measure.

PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

SARS-CoV-2 strain included Omicron XBB.1.5 antibody. Seroresponse was defined as an increase from below the LLOQ to ≥4 * LLOQ if Baseline neutralizing antibody (nAb) level was < LLOQ, or ≥4-fold rise if Baseline nAb level was ≥ LLOQ. LLOQ = 38 and ULOQ = 6960 AU/mL for SARS-CoV-2 Omicron XBB.1.5 antibody. Arms based on the applicable vaccine for this Outcome Measure.

PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Antibody values reported as below LLOQ were replaced by 0.5 * LLOQ. Values greater than ULOQ were converted to ULOQ. LLOQ = 10 and ULOQ = 640 for Influenza A H1N1 and Influenza A H3N2 antibody, LLOQ = 10 and ULOQ = 320 for Influenza B/ Victoria, and LLOQ = 10 and ULOQ = 640 for Influenza B/Yamagata antibody. 95% CI was calculated based on t-distribution of log-transformed values for GM titer, then back transformed to original scale for presentation. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. 'Number analyzed' = participants evaluable for specified category. Arms based on the applicable vaccine for this Outcome Measure.

SARS-CoV-2 strain included BA.4/5 and D614G antibody. Antibody values reported as below LLOQ were replaced by 0.5 * LLOQ. Values greater than ULOQ were converted to ULOQ. LLOQ = 53 and ULOQ = 71376 for SARS-CoV-2 BA.4/5 antibody and LLOQ = 74.1 and ULOQ = 184317 for SARS-CoV-2 D614G antibody. 95% CI was calculated based on t-distribution of log-transformed values for GM titer, then back transformed to original scale for presentation. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. 'Number analyzed' = participants evaluable for specified category. Arms based on the applicable vaccine for this Outcome Measure.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Antibody values reported as below LLOQ were replaced by 0.5 * LLOQ. Values greater than ULOQ were converted to ULOQ. LLOQ = 10 and ULOQ = 640 for Influenza A H1N1 and Influenza A H3N2 antibody, LLOQ = 10 and ULOQ = 320 for Influenza B/Victoria, and LLOQ = 10 and ULOQ = 640 for Influenza B/Yamagata antibody. 95% CI was calculated based on t-distribution of log-transformed values for GMFR, then back transformed to original scale for presentation. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. 'Number analyzed' = participants evaluable for specified category. Arms based on the applicable vaccine for this Outcome Measure.

SARS-CoV-2 strain included BA.4/5 and D614G antibody. Antibody values reported as below LLOQ were replaced by 0.5 * LLOQ. Values greater than ULOQ were converted to ULOQ. LLOQ = 53 and ULOQ = 71376 for SARS-CoV-2 BA.4/5 antibody and LLOQ = 74.1 and ULOQ = 184317 for SARS-CoV-2 D614G antibody. 95% CI was calculated based on t-distribution of log-transformed values for GMFR, then back transformed to original scale for presentation. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. 'Number analyzed' = participants evaluable for specified category. Arms based on the applicable vaccine for this Outcome Measure.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Seroconversion was defined as a pre-vaccination HAI titer < 1:10 and a post-vaccination HAI titer ≥1:40 or a pre-vaccination HAI titer ≥1:10 and a minimum 4-fold rise in post vaccination HAI antibody titer. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. 'Number analyzed' = participants evaluable for specified category. Arms based on the applicable vaccine for this Outcome Measure.

SARS-CoV-2 strain included BA.4/5 and D614G antibody. Seroresponse was defined as an increase from below the LLOQ to ≥4 x LLOQ if baseline nAb level was \

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. 'Number analyzed' = participants evaluable for specified category. Arms based on the applicable vaccine for this Outcome Measure.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Antibody values reported as below the LLOQ were replaced by 0.5 * LLOQ. Values greater than the ULOQ were converted to the ULOQ. LLOQ = 10 and ULOQ = 3620 for Influenza A H1N1 antibody, LLOQ = 10 and ULOQ = 5120 for Influenza A H3N2 antibody, LLOQ = 10 and ULOQ = 1356 for Influenza B/Victoria-lineage antibody, and LLOQ = 10 and ULOQ = 1280 for Influenza B/Yamagata-lineage antibody. 95% CI was calculated based on the t-distribution of the log-transformed values for GM titer, then back transformed to the original scale for presentation. Arms based on the applicable vaccine for this Outcome Measure.

PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response. 'Number analyzed' = participants evaluable for specified category.

SARS-CoV-2 strain included Omicron XBB.1.5 antibody. Antibody values reported as below the LLOQ are replaced by 0.5 * LLOQ. Values greater than the ULOQ are converted to the ULOQ. LLOQ = 38 and ULOQ = 6960 arbitrary units (AU)/milliliter (mL) for SARS-CoV-2 Omicron XBB.1.5 antibody. 95% CI was calculated based on the t-distribution of the log-transformed values for GM concentration, then back transformed to the original scale for presentation. Arms based on the applicable vaccine for this Outcome Measure.

PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response. 'Number analyzed' = participants evaluable for specified category.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Antibody values reported as below LLOQ replaced by 0.5 * LLOQ. Values greater than ULOQ converted to ULOQ. LLOQ= 10, ULOQ= 3620 for Influenza A H1N1, LLOQ= 10, ULOQ= 5120 for Influenza A H3N2, LLOQ= 10, ULOQ= 1356 for Influenza B/Victoria-lineage, and LLOQ= 10, ULOQ= 1280 for Influenza B/Yamagata-lineage. 95% CI was calculated based on t-distribution of log-transformed values for GMFR, then back transformed to original scale for presentation. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. Arms based on the applicable vaccine for this Outcome Measure.

SARS-CoV-2 strain included Omicron XBB.1.5 antibody. Antibody values reported as below the LLOQ are replaced by 0.5 * LLOQ. Values greater than the ULOQ are converted to the ULOQ. LLOQ = 38 and ULOQ = 6960 AU/mL for SARS-CoV-2 Omicron XBB.1.5 antibody. 95% CI was calculated based on the t-distribution of the log-transformed values for GMFR values, then back transformed to the original scale for presentation. PP Set: all randomized participants who received study drug, complied with injection schedule, complied with timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. Arms based on the applicable vaccine for this Outcome Measure.

Influenza A strains included H1N1 and H3N2 and influenza B strains included Victoria-lineage and Yamagata-lineage. Seroconversion was defined as a pre-vaccination HAI titer <1:10 and a post-vaccination HAI titer ≥1:40 or a pre-vaccination HAI titer ≥1:10 and a minimum 4-fold rise in post-vaccination HAI antibody titer. PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. Arms based on the applicable vaccine for this Outcome Measure.

SARS-CoV-2 strain included Omicron XBB.1.5 antibody. Seroresponse was defined as an increase from below the LLOQ to ≥4 * LLOQ if Baseline nAb level was < LLOQ, or ≥4-fold rise if Baseline nAb level was ≥ LLOQ. PP Set included all randomized participants who received the study intervention, complied with the injection schedule, complied with the timings of immunogenicity blood sampling to have a Baseline and at least 1 post-injection assessment at Day 29, had no documented infection of either influenza or SARS-CoV-2 on Day 1 and up to Day 29, had no major dosing error, and had no major protocol deviations or conditions/medications that affected the immune response.

PP Set. 'Overall number of participants analyzed' = participants evaluable for this outcome measure. Arms based on the applicable vaccine for this Outcome Measure.