GMTs of HI antibodies were measured using hemagglutination inhibition (HAI) assay against each of four influenza vaccine strains (A/Victoria \[H1N1\], A/Cambodia \[H3N2\], B/Victoria \[B/Victoria\] and B/Phuket \[B/Yamagata\]). This outcome measure was planned to be analyzed for specified arms only. PPII=Per-protocol influenza immunogenicity.

GMCs of antibody titers measured by S-ELISA at 28 days after administration of Ad26.COV2.S vaccine was reported. This outcome measure was planned to be analyzed for specified arms only. Seronegative participants (at Day 1) who became serology positive during the study, participants with positive molecular test for severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) and major protocol deviation were excluded from PPSI analysis.

Geometric mean concentration of SARS-CoV-2 S protein binding antibodies measured by ELISA were reported. As per planned analysis, the data were analyzed and reported combined for the main study and sub-study.

Geometric mean concentration of SARS-CoV-2 S protein binding antibodies measured by ELISA were reported. As per planned analysis, the data were analyzed and reported combined for the main study and sub-study.

Number of adult participants with solicited local AEs for 7 days post first vaccination was reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited AEs were used to assess the reactogenicity of the study vaccine and were pre-defined as local (at the injection site) AEs for which participants were specifically asked and which were noted by participants in their reactogenicity diary for 7 days post first vaccination (day of first vaccination and the subsequent 7 days). Solicited local AEs are injection site pain/tenderness, erythema, swelling at the vaccination site.

Number of adult participants with solicited systemic AEs for 7 days post first vaccination was reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited AEs were used to assess the reactogenicity of the study vaccine and were predefined as systemic AEs for which participants were specifically asked and which were noted by participants in their reactogenicity diary for 7 days post first vaccination. Participants were instructed on how to note signs and symptoms in the diary on a daily basis for 7 days post first vaccination (day of first vaccination and the subsequent 7 days) for the following solicited systemic AEs: fatigue, headache, nausea, myalgia.

Number of adult participants with unsolicited AEs for 28 days post first vaccination was reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were defined as AEs for which the participants were not specifically questioned in the participant's reactogenicity diary.

Number of adult participants with SAEs from first vaccination until EOS were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. SAEs were defined as any untoward medical occurrence that at any dose results in any of the following outcomes: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly/birth defect; suspected transmission of any infectious agent via a medicinal product or medically important.

Number of adult participants with AESIs from first vaccination until EOS were reported. Thrombosis with thrombocytopenia syndrome (TTS) in adults was considered an AESI in this study. TTS is a syndrome characterized by a combination of both a thrombotic event and thrombocytopenia.

Number of adult participants with MAAEs until 6 months post first vaccination was reported. MAAEs were defined as AEs with medically attended visits including hospital, emergency room, urgent care clinic, or other visits to or from medical personnel for any reason. Routine study visits were not considered medically attended visits. New onset of chronic diseases was collected as part of the MAAEs.

Number of adult participants with AEs leading to study discontinuation were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. All AEs leading to discontinuation from the study (regardless of the causal relationship) were reported for all adult participants from the moment of first vaccination until completion of the participant's last study-related procedure.

Serological response to vaccination as measured by S-ELISA in adult participants 28 days post first vaccination was reported.

Number of participants with solicited local AEs for 7 days after vaccination 1 in Cohorts 1a and 1b were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after vaccination 2 in Cohorts 1a and 1b were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after ad hoc booster vaccination in Cohorts 1a and 1b were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after vaccination 1 in Cohorts 2a and 2b were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after booster vaccination 1 in Cohort 2a were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after booster vaccination 2 in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after ad hoc booster vaccination in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after Vaccination 2 in Cohort 2b were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after booster vaccination 1 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after booster Vaccination 2 in Cohort 2b were reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited local AEs for 7 days after ad hoc booster vaccination in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, are used to assess the reactogenicity of the study vaccine and are pre-defined local (injection site).

Number of participants with solicited systemic AEs for 7 days after vaccination 1 in Cohorts 1a and 1b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after vaccination 2 in Cohorts 1a and 1b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after ad hoc booster vaccination in Cohorts 1a and 1b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post Ad Hoc Booster Vaccination (day of Ad hoc booster vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after vaccination 1 in Cohorts 2a and 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days post booster vaccination 1 in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after booster vaccination 2 in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after ad hoc booster vaccination in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post adhoc booster vaccination (day of ad hoc booster vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after vaccination 2 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after booster vaccination 1 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after booster vaccination 2 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited systemic AEs for 7 days after ad hoc booster vaccination in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post ad hoc booster vaccination (day of ad hoc booster vaccination and the subsequent 7 days).

Number of participants with solicited local AEs for 7 days after vaccination 1 in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, were used to assess the reactogenicity of the study vaccine and were pre-defined local (injection site).

Number of participants with solicited systemic AEs for 7 days after vaccination 1 in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited local AEs for 7 days after vaccination 2 in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, were used to assess the reactogenicity of the study vaccine and were pre-defined local (injection site).

Number of participants with solicited systemic AEs for 7 days after vaccination 2 in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post-vaccination (day of vaccination and the subsequent 7 days).

Number of participants with solicited local AEs for 7 days after ad hoc booster vaccination in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Solicited local (injection site) AEs that included injection site pain/tenderness, erythema and swelling at the study vaccine injection site, were used to assess the reactogenicity of the study vaccine and were pre-defined local (injection site).

Number of participants with solicited systemic AEs for 7 days after ad hoc booster vaccination in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Systemic events included events such as fatigue, headache, nausea, and myalgia, for which participants were specifically questioned and which will be noted by participants in their participant diary for 7 days post ad hoc booster vaccination (day of ad hoc booster vaccination and the subsequent 7 days).

Number of participants with unsolicited AEs after vaccination 1 in Cohorts 1a and 1b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after vaccination 2 in Cohorts 1a and 1b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after ad hoc booster vaccination in Cohorts 1a and 1b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after vaccination 1 in Cohorts 2a and 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after booster 1 vaccination in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after booster vaccination 2 in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after ad hoc booster vaccination in Cohort 2a were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs after vaccination 1 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs 28 days after booster vaccination 1 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs 28 days after booster vaccination 2 in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs 28 days after ad hoc booster vaccination in Cohort 2b were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs 28 days after vaccination 1 in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs 28 days after vaccination 2 in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

Number of participants with unsolicited AEs 28 days after ad hoc booster vaccination in Cohort 3 were reported. An AE was any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Unsolicited AEs were all AEs for which the participant is not specifically questioned in the participant diary.

An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. An SAE is an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly/birth defect; suspected transmission of any infectious agent via a medicinal product or medically important.

An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. An SAE is an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly/birth defect; suspected transmission of any infectious agent via a medicinal product or medically important.

Number of participants with AESIs was reported. AESIs were significant AEs that were judged to be of special interest because of clinical importance, known or suspected class effects, or based on nonclinical signals. Thrombosis with Thrombocytopenia Syndrome (TTS), a syndrome characterized by a combination of both a thrombotic event and thrombocytopenia, was considered to be an AESI in this study. A suspected TTS case was defined as: Thrombotic events: suspected deep vessel venous or arterial thrombotic events; Thrombocytopenia, defined as platelet count below 150,000/microliter.

Number of participants with AESIs was reported. AESIs were significant AEs that were judged to be of special interest because of clinical importance, known or suspected class effects, or based on nonclinical signals. Thrombosis with Thrombocytopenia Syndrome (TTS), a syndrome characterized by a combination of both a thrombotic event and thrombocytopenia, was considered to be an AESI in this study. A suspected TTS case was defined as: Thrombotic events: suspected deep vessel venous or arterial thrombotic events; Thrombocytopenia, defined as platelet count below 150,000/microliter.