Blood was collected for HAI assay which was conducted with the 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 21 days post second study vaccination (Day 43).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 and stratum from the available results at 21 days post study vaccination (Day 142).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at 21 days post second study vaccination (Day 43).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. The geometric mean titer was calculated for each study arm from the available results at 21 days post second study vaccination (Day 142).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

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.

The Safety Analysis population includes all participants who received study vaccination.

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.

The Safety Analysis population includes all participants who received study vaccination.

Laboratory parameters include alanine aminotransferase (ALT), bilirubin, creatinine, hemoglobin, platelets and white blood cells (WBC). Thresholds for adverse events were considered as ALT 44 IU/L or greater (female) or 61 IU/L or greater (male); bilirubin 1.30 mg/dL or greater; creatinine 1.1 mg/dL or greater (female) or 1.4 mg/dL or greater (male); hemoglobin 11.4 g/dL or lower (female) or 12.4 g/dL or lower (male); platelets 139 x10^3/µL or below or 416 x10^3/µL or greater; or WBC or 3.9 x10^3/µL or lower or 10.6 x10^3/µL or higher.

The Safety Analysis population includes all participants who received study vaccination. Participants with at least one lab result reported for Day 8 post first vaccination were included for this outcome measure.

Laboratory parameters include alanine aminotransferase (ALT), bilirubin, creatinine, hemoglobin, platelets and white blood cells (WBC). Thresholds for adverse events were considered as ALT 44 IU/L or greater (female) or 61 IU/L or greater (male); bilirubin 1.30 mg/dL or greater; creatinine 1.1 mg/dL or greater (female) or 1.4 mg/dL or greater (male); hemoglobin 11.4 g/dL or lower (female) or 12.4 g/dL or lower (male); platelets 139 x10^3/µL or below or 416 x10^3/µL or greater; or WBC or 3.9 x10^3/µL or lower or 10.6 x10^3/µL or higher.

The Safety Analysis population includes all participants who received study vaccination. Participants with at least one lab result reported for Day 8 post second vaccination were included for this outcome measure.

Laboratory parameters include alanine aminotransferase (ALT), bilirubin, creatinine, hemoglobin, platelets and white blood cells (WBC). Thresholds for adverse events were considered as ALT 44 IU/L or greater (female) or 61 IU/L or greater (male); bilirubin 1.30 mg/dL or greater; creatinine 1.1 mg/dL or greater (female) or 1.4 mg/dL or greater (male); hemoglobin 11.4 g/dL or lower (female) or 12.4 g/dL or lower (male); platelets 139 x10^3/µL or below or 416 x10^3/µL or greater; or WBC or 3.9 x10^3/µL or lower or 10.6 x10^3/µL or higher.

The Safety Analysis population includes all participants who received study vaccination. Participants with at least one lab result reported for Day 8 post second vaccination were included for this outcome measure.

Injection site 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). Participants are considered reporting the injection site 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 study vaccination.

Injection site 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). Participants are considered reporting the injection site AE if they reported mild or greater severity at any time during the 8 days at or following the second vaccination.

The Safety Analysis population includes all participants who received study vaccination.

Injection site 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). Participants are considered reporting the injection site AE if they reported mild or greater severity at any time during the 8 days at or following the second vaccination.

The Safety Analysis population includes all participants who received study vaccination.

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 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 study vaccination.

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 systemic AE if they reported mild or greater severity at any time during the 8 days at or following the second vaccination.

The Safety Analysis population includes all participants who received study vaccination.

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 systemic AE if they reported mild or greater severity at any time during the 8 days at or following the second vaccination.

The Safety Analysis population includes all participants who received study vaccination.

Blood was collected for the HAI assay conducted with the H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. The percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results at 21 days post second study vaccination (Day 43).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for the HAI assay conducted with the H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. The percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results at 21 days post second study vaccination (Day 142 ).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for the Neutralizing assay conducted with the H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. The percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results at 21 days post second study vaccination (Day 43).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for the Neutralizing assay conducted with the H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. The percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results at 21 days post second study vaccination (Day 142).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for the HAI assay conducted with the 2017 H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. Seroconversion was defined as HAI pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 21 days after second study vaccination is Day 43.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for the HAI assay conducted with the 2017 H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. Seroconversion was defined as HAI pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 21 days after second study vaccination is Day 142.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for the Neutralizing assay conducted with the 2017 H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. Seroconversion was defined as Neut pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 21 days after second study vaccination is Day 43.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for the Neutralizing assay conducted with the 2017 H7N9 vaccine virus as the antigen. Each sample was tested at least twice per the laboratory's standard operating procedure, and the geometric mean of the replicate results was calculated as that sample's result. Seroconversion was defined as Neut pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 21 days after second study vaccination is Day 142.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 immediately prior to the first study vaccination (Day 1).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 21 days post first study vaccination (Day 22).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 180 days post second study vaccination (Day 202).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 immediately prior to second study vaccination (Day 121).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 180 days post second study vaccination (Day 301).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 immediately prior to the first study vaccination (Day 1).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 21 days post first study vaccination (Day 22).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 180 days post second study vaccination (Day 202).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 immediately prior to second study vaccination (Day 121).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 180 days post second study vaccination (Day 301).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

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) throughout the duration of the study.

The Safety Analysis population includes all participants who received study vaccination

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) throughout the duration of the study.

The Safety Analysis population includes all participants who received study vaccination.

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 21 days after the first study vaccination.

The Safety Analysis population includes all participants who received study vaccination.

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 21 days after the second study vaccination.

The Safety Analysis population includes all participants who received study vaccination.

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 21 days after the second study vaccination.

The Safety Analysis population includes all participants who received study vaccination.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as HAI pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 21 days after first study vaccination is Day 22.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as HAI pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 180 days after second study vaccination is Day 202.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as HAI pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. Immediately prior to second study vaccination is Day 121.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as HAI pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 180 days after second study vaccination is Day 301.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as Neut pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 21 days after first study vaccination is Day 22.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as Neut pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 180 days after second study vaccination is Day 202.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as Neut pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. Immediately prior to second study vaccination is Day 121.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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. Seroconversion was defined as Neut pre-vaccination titer <1:10 and post-vaccination titer >= 1:40 or pre-vaccination titer >= 1:10 and minimum 4-fold rise in post-vaccination antibody titer. 180 days after second study vaccination is Day 301.

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results immediately prior to the first study vaccination (Day 1).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results at 21 days post first study vaccination (Day 22).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results at 180 days post first study vaccination (Day 202).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results immediately prior to second study vaccination (Day 121).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for HAI assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with HAI titer >= 1:40 was calculated for each study arm from the available results at 180 days post first study vaccination (Day 301).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.

Blood was collected for Neutralizing assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results immediately prior to the first study vaccination (Day 1).

The modified intent-to-treat (mITT) population includes all participants who received study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results at 21 days post first study vaccination (Day 22).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results at 180 days post first study vaccination (Day 202).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for NEUT assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results immediately prior to second study vaccination (Day 121).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.

Blood was collected for Neut assay which was conducted with the 2013 and 2017 H7N9 vaccine viruses as the antigens. Each sample was tested at least 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 percentage of participants with Neut titer >= 1:40 was calculated for each study arm from the available results at 180 days post second study vaccination (Day 301).

The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for Neut antibody assays for which valid results were reported.