Local adverse events (AEs) solicited on a memory aid provided to participants included Pain, Tenderness, Itching/Pruritus, Ecchymosis/Bruising (functional grade based on interference with daily activities), Ecchymosis/Bruising (any measured value >0mm), Erythema/Redness (functional grade), Erythema/ Redness (any measured value >0mm), Induration/Swelling (functional grade), and Induration/Swelling (any measured value >0mm).

Systemic AEs solicited on a memory aid provided to participants included Elevated Oral Temperature, Feverishness, Fatigue, Malaise, Myalgia, Arthralgia, Headache, and Nausea. Participants are considered reporting the local or systemic AE if they reported mild or greater severity at any time during the 8 days at or following the first vaccination.

The Safety Analysis population includes all participants who received the first study vaccination. Analyses for the safety population are based on vaccine actually received. One participant randomized to Flublok + AF03 group received Flublok due to a pharmacy error and is analyzed in the Flublok group.

Adverse events were defined as any untoward medical occurrence in a participant administered a pharmaceutical product regardless of its causal relationship to the study treatment. Non-serious AEs were collected from participants at follow up visits through 28 days after the first study vaccination while serious adverse events (SAEs) were collected at follow up visits through approximately 12 months after the first study vaccination. Adverse events were MedDRA coded and are summarized by MedDRA System Organ Class (SOC).

The Safety Analysis population includes all participants who received the first study vaccination. Analyses for the safety population are based on vaccine actually received. One participant randomized to Flublok + AF03 group received Flublok due to a pharmacy error and is analyzed in the Flublok group.

SAEs included any untoward medical occurrence that resulted in death; was life threatening; was a persistent/significant disability/incapacity; required inpatient hospitalization or prolongation or a congenital anomaly/birth defect. All SAEs were reported from time of first study vaccination through approximately 12 months after the first study vaccination.

The Safety Analysis population includes all participants who received the first study vaccination. Analyses for the safety population are based on vaccine actually received. One participant randomized to Flublok + AF03 group received Flublok due to a pharmacy error and is analyzed in the Flublok group.

Laboratory parameters include white blood cells (WBC), hemoglobin, platelets, alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, Gamma-Glutamyl Transferase (GGT), alkaline phosphatase (ALP), amylase, lipase, and creatinine. Thresholds for adverse events were considered WBC of 3.90 x10^3/uL or lower or 10.60 x10^3/uL or higher; hemoglobin 11.4 g/dL or lower (female) or 12.4 g/dL or lower (male); platelets 139 x10^3/uL or below or 416 x10^3/uL or greater when using EDTA tubes or platelets 124 x10^3/uL or below or 550 x10^3/uL or greater when using Citrate tubes; ALT 44 IU/L or greater (female) or 61 IU/L or greater (male); AST 37 IU/L or greater (female) or 44 IU/L or greater (male); bilirubin 1.30 mg/dL or greater; GGT 33 IU/L or greater (female) or 50 IU/L or greater (male); ALP 116 IU/L or greater; amylase 122 IU/L or greater; lipase 61 IU/L or greater; creatinine 1.1 mg/dL or greater (female) or 1.4 mg/dL or greater (male).

The Safety Analysis population includes all participants who received the first study vaccination. Analyses for the safety population are based on vaccine actually received. One participant randomized to Flublok + AF03 group received Flublok due to a pharmacy error and is analyzed in the Flublok group.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1 and Day 29 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1 and Day 29 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. HAI seroconversion was defined as either a pre-vaccination titer < 1:10 and a post-vaccination titer >= 1:40 or a pre-vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises from baseline were calculated as the Day 29 titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1 and Day 29 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1 and Day 29 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. NAI seroconversion was defined as >4 four-fold rise in post-vaccination antibody titer at Day 29.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises from baseline were calculated as the Day 29 titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 1 and Day 29 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 1 and Day 29 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Neut seroconversion was defined as either a pre-vaccination titer < 1:10 and a post-vaccination titer >= 1:40 or a pre-vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Fold-rises from baseline were calculated as the Day 29 titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Participants were queried at each visit for the occurrence of adverse events of special interest (AESIs) through approximately 12 months following the first study vaccination. AESIs include reports of tearing, dry mouth, and dry eyes.

The Safety Analysis population includes all participants who received study vaccination. Analyses for the safety population are based on vaccine actually received. One participant randomized to Flublok + AF03 group received Flublok due to a pharmacy error and is analyzed in the Flublok group.

Participants were queried at each visit for the occurrence of medically-attended adverse events (MAAEs), including new-onset chronic medical conditions (NOCMCs) and potentially immune-mediated medical conditions (PIMMCs) through approximately 12 months following the first study vaccination.

The Safety Analysis population includes all participants who received the first study vaccination. Analyses for the safety population are based on vaccine actually received. One participant randomized to Flublok + AF03 group received Flublok due to a pharmacy error and is analyzed in the Flublok group.

Blood was collected for HAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 90 and Day 118 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 90 and Day 118 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. HAI seroconversion was defined as either a pre-second vaccination titer < 1:10 and a post- second vaccination titer >= 1:40 or a pre-second vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises at Day 118 were calculated as the Day 118 titer divided by the Day 90 titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 90 and Day 118 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 90 and Day 118 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

The unadjuvanted Fluzone study arm is considered a reference group for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. NAI seroconversion was defined as >4 four-fold rise in post-vaccination antibody titer at Day 90 through Day 118.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises at Day 118 were calculated as the Day 118 titer divided by the Day 90 titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 90 and Day 118 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 90 and Day 118 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Neut seroconversion was defined as either a pre-second vaccination titer < 1:10 and a post-second vaccination titer >= 1:40 or a pre-second vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2019/2020 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Fold-rises at Day 118 were calculated as the Day 118 titer divided by the Day 90 titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 8, Day 57, Day 90, and Day 118 Post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 8, Day 57, Day 90, and Day 118 Post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. HAI seroconversion was defined as either a pre-vaccination titer < 1:10 and a post-vaccination titer >= 1:40 or a pre-vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises from baseline were calculated as the Day 8 (or Day 57, Day 90, Day 118) titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 8, Day 57, Day 90, and Day 118 Post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 8, Day 57, Day 90, and Day 118 Post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

The unadjuvanted Fluzone study arm is considered a reference group for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. NAI seroconversion was defined as >4 four-fold rise in post-vaccination antibody titer at Day 8, 57, 90, and 118.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises from baseline were calculated as the Day 8 (or Day 57, Day 90, Day 118) titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which is a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 8, Day 57, Day 90, and Day 118 Post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which is a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 8, Day 57, Day 90, and Day 118 Post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which is a geometric mean titer of the replicates was reported by the lab. Neut seroconversion was defined as either a pre-vaccination titer < 1:10 and a post-vaccination titer >= 1:40 or a pre-vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which is a geometric mean titer of the replicates was reported by the lab.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the 2018/2019 QIV viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Fold-rises from baseline were calculated as the Day 8 (or Day 57, Day 90, Day 118) titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood sample for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1, Day 8, Day 29, Day 57, Day 90, and Day 118 post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1, Day 8, Day 29, Day 57, Day 90, and Day 118 post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms was calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. HAI seroconversion was defined as either a pre-vaccination titer < 1:10 and a post-vaccination titer >= 1:40 or a pre-vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for HAI assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises from baseline were calculated as the Day 8 (or Day 29, Day 57, Day 90, Day 118) titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid HAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the heterologous N1 and N2 NA viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1, Day 8, Day 29, Day 57, Day 90, and Day 118 Post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the heterologous N1 and N2 NA viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at Day 1, Day 8, Day 29, Day 57, Day 90, and Day 118 Post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

The unadjuvanted Fluzone study arm is considered a reference group for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the heterologous N1 and N2 NA viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. NAI seroconversion was defined as >4 four-fold rise in post-vaccination antibody titer at Day 8, 29, 57, 90, and 118.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for NAI assay which was conducted with the heterologous N1 and N2 NA viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, and the geometric mean of the replicate results of each antigen was calculated as that sample's result. Fold-rises from baseline were calculated as the Day 8 (or Day 29, Day 57, Day 90, Day 118) titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid NAI results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 1, Day 8, Day 29, Day 57, Day 90, and Day 118 Post first study vaccination.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. The geometric mean titer was calculated for each study arm from the available results at Day 1, Day 8, Day 29, Day 57, Day 90, and Day 118 Post first study vaccination and the ratio of these GMTs between adjuvanted and unadjuvanted study arms were calculated.

Unadjuvanted Fluzone and Flublok study arms are considered as reference groups for the analysis of ratio of GMTs.

Ratio of GMTs is defined as the ratio of the GMT from the adjuvanted group divided by the GMT from the corresponding unadjuvanted group.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Neut seroconversion was defined as either a pre-vaccination titer < 1:10 and a post-vaccination titer >= 1:40 or a pre-vaccination titer >= 1:10 and a minimum four-fold rise in post-vaccination antibody titer.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.

Blood was collected for Neut assay which was conducted with the heterologous H1 and H3 influenza viruses as the antigens. Each sample was tested twice per antigen per the laboratory's standard operating procedure, but only one result which a geometric mean titer of the replicates was reported by the lab. Fold-rises from baseline were calculated as the Day 8 (or Day 29, Day 57, Day 90, Day 118) titer divided by the baseline titers for each participant. The geometric mean of these fold rises was then calculated to obtain the GMFR.

The modified intent-to-treat (mITT) population includes all randomized participants who received the first study vaccination and contributed at least one post-first study vaccination venous blood samples for immunogenicity testing (HAI, NAI or Neut antibody assays) for which valid Neut results were reported. For analyses using the mITT population, participants were grouped based on randomized study arm.