Study treatment arm: per protocol (PP) set for immunogenicity, participants in the Modified Intent-To-Treat Analysis Set (mITT) who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. As pre-specified, data for groups 2a & 2b were collected and are reported pooled as a combined group.

Seroconversion was defined as either a pre-vaccination titer below the lower limit of quantitation (LLOQ) and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer.

Study treatment arm: PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. As pre-specified, data for groups 2a &2b were collected and are reported pooled as a combined group.

Influenza vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. Overall number of participants analyzed = participants evaluable for this outcome measure. Number analyzed = participants evaluable at the specified timepoint.

GMFR is reported as a ratio to Day 1.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. Overall number of participants analyzed = participants evaluable for this outcome measure. Number analyzed = participants evaluable at the specified timepoint.

Seroconversion was defined as either a pre-vaccination titer below the LLOQ and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata. GMFR is reported as a ratio to Day 1.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Seroconversion was defined as either a pre-vaccination titer below the LLOQ and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer. Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. Overall number of participants analyzed = number evaluable for the outcome measure. Number analyzed = participants evaluable at the specified timepoint.

GMFR is reported as a ratio to Day 1.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. Overall number of participants analyzed = number evaluable for the outcome measure. Number analyzed = participants evaluable at the specified timepoint.

Seroconversion was defined as either a pre-vaccination titer below the LLOQ and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata. GMFR is reported as a ratio to Day 1.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Seroconversion was defined as either a pre-vaccination titer below the LLOQ and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer. Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Vaccine strains analyzed for this outcome measure were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.

Systemic AEs: fatigue, headache, myalgia, arthralgia, nausea, dizziness, chills, and fever. Solicited local (injection site) AEs: injection site pain, erythema, and swelling. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.

Safety Analysis Set (SAF), which included all participants in the Exposed Set (participants who received at least one dose of a study vaccine) who provided any evaluable post-vaccination reactogenicity and/or safety data. Number analyzed = participants evaluable at the specified timepoint.

An unsolicited AE was an AE that was not listed as 'solicited' and was defined as any spontaneously occurring AE (serious and non-serious). Potential unsolicited AEs may have been medically attended (defined as symptoms or illnesses requiring hospitalization, or emergency room visit, or visit to/by a healthcare provider) or were of concern to the participants. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.

Safety Analysis Set, which included all participants in the Exposed Set (participants who received at least one dose of a study vaccine) who provided any evaluable post-vaccination reactogenicity and/or safety data. Overall number of participants analyzed = participants evaluable for the outcome measure. Number analyzed = participants evaluable at the specified timepoint.

SAEs were defined as any event that resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in a persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, a congenital anomaly or birth defect, or was an important medical event. A MAAE was an AE that led to an unscheduled visit (including a telemedicine visit) to a healthcare practitioner. AESIs were defined as AEs potentially associated with Coronavirus Disease 2019 (COVID-19) and COVID-19 vaccines. Number of participants with AEs leading to early termination included AEs leading to death. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.

Safety Analysis Set, which included all participants in the Exposed Set (participants who received at least one dose of a study vaccine) who provided any evaluable post-vaccination reactogenicity and/or safety data.