A Study of Ad26.COV2.S Administered as Booster Vaccination in Adults Who Have Previously Received Primary Vaccination With Ad26.COV2.S or BNT162b2

GMTs of neutralizing antibodies against SARS-CoV-2 original strain 14 days after Ad26.COV2.S booster vaccination after completing primary vaccination with Ad26.COV2.S (5×10\^10 vp dose level) were reported. GMT against original strain was assessed by virus neutralization assay (VNA).

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., on Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against SARS-CoV-2 original strain 28 days after primary vaccination with Ad26.COV2.S (5×10\^10 vp dose level) were reported. GMT against original strain was assessed by VNA.

Time frame: 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against leading variant of high consequence or concern (delta variant) 14 days After Ad26.COV2.S booster vaccination (5\*10\^10 vp dose level) after completing primary vaccination with Ad26.COV2.S were reported. GMT against Delta Variant was assessed by VNA. As specified in the protocol, data for this outcome measure was not collected and analyzed for Cohort 1: Ad26.COV2.S 2.5\*10\^10 vp and 1\*10\^10 vp participants.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against the leading variant of high consequence or concern (delta variant) 28 days after primary vaccination with Ad26.COV2.S (5\*10\^10 vp dose level) were reported. GMT against Delta variant was assessed by VNA. As specified in the protocol, data for this outcome measure was not collected and analyzed for Cohort 1: Ad26.COV2.S 2.5\*10\^10 vp and 1\*10\^10 vp participants. Lower limit of Quantification (LLOQ) was 65.

Time frame: 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 leading variant of high consequence or concern (delta variant) 28 days after primary vaccination with Ad26.COV2.S (5\*10\^10 vp dose level) were reported. A participant was considered a responder if one or both of the following conditions were satisfied: (1) Pre-dose titer \<LLOQ and post-vaccination titer \>=4\*LLOQ or (2) Pre-dose titer \>LLOQ and post-vaccination titer \>=4\*pre-dose 1 titer value. As specified in the protocol, data for this outcome measure was not collected and analyzed for Cohort 1: Ad26.COV2.S 2.5\*10\^10 vp and 1\*10\^10 vp participants.

Time frame: 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 original strain (Wuhan, 2019, whole genome sequence) 14 days after Ad26.COV2.S booster vaccination after completing primary vaccination with Ad26.COV2.S was reported. A participant was considered a responder if one or both of the following conditions were satisfied: (1) Pre-booster titer less than (\<) lower limit of quantification (LLOQ) and post-booster titer greater than or equal to (\>=) 4\*LLOQ or (2) Pre-booster titer greater than (\>) LLOQ and post-booster titer \>=4\*pre-booster titer value.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., on Day 15)

Population: Non-inferiority (NI) analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 original strain 28 days after primary vaccination with Ad26.COV2.S (5×10\^10 vp dose level) were reported. A participant was considered a responder if one or both of the following conditions were satisfied: (1) Pre-dose titer \<LLOQ and post-vaccination titer \>=4\*LLOQ or (2) Pre-dose titer \>LLOQ and post-vaccination titer \>=4\*pre-dose 1 titer value.

Time frame: 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against leading variant of high consequence or concern (delta variant) 14 days after Ad26.COV2.S booster vaccination (5\*10\^10 vp Dose Level) after completing primary vaccination with Ad26.COV2.S were reported. A participant was considered a responder if one or both of the following conditions were satisfied: (1) Pre-booster titer \<LLOQ and post-booster titer \>=4\*LLOQ or (2) Pre-booster titer \>LLOQ and post-booster titer \>=4\*pre-booster titer value. As specified in the protocol, data for this outcome measure was not collected and analyzed for Cohort 1: Ad26.COV2.S 2.5\*10\^10 vp and 1\*10\^10 vp participants.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against SARS-CoV-2 original strain 14 days after Ad26.COV2.S booster vaccination after completing 2-dose primary vaccination with BNT162b2 were reported. GMT against original strain was assessed by VNA.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against SARS-CoV-2 original strain 2 weeks to 2 months after completing 2-dose primary vaccination with BNT162b2 were reported. GMT against original strain was assessed by VNA.

Time frame: 2 weeks to 2 months after primary vaccination with BNT162b2 (up to 1.5 months)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Antibody GMTs of neutralizing antibodies against the SARS-CoV-2 leading variant of high consequence or concern (Delta variant) 2 weeks to 2 months after completing 2-dose primary vaccination with BNT162b2 were reported. GMT against delta variant was assessed by VNA.

Time frame: 2 weeks to 2 months after primary vaccination with BNT162b2 (up to 1.5 months)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Antibody GMTs of neutralizing antibodies against the SARS-CoV-2 leading variant of high consequence or concern (Delta variant) 14 days after booster vaccination after completing 2-dose primary vaccination with BNT162b2 were reported. GMT against delta variant was assessed by VNA. As specified in the protocol, data for this outcome measure was not collected and analyzed for Cohort 2: Ad26.COV2.S 2.5\*10\^10 vp and 1\*10\^10 vp participants.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 leading variant of high consequence or concern (Delta) 14 days after booster vaccination (5\*10\^10 vp dose level) after completing 2-dose primary vaccination with BNT162b2 were reported. A participant was considered a responder if at least one of the following conditions was satisfied: (1) If pre-booster 1 titer \<LLOQ, then post-booster titer \>=4\*LLOQ or (2) If pre-booster 1 titer \>LLOQ, then post-booster titer \>=4\*pre-booster value (titer). As specified in the protocol, data for this outcome measure was not collected and analyzed for Cohort 2: Ad26.COV2.S 2.5\*10\^10 vp and 1\*10\^10 vp participants.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 original strain, 14 days after Ad26.COV2.S booster vaccination after completing 2-dose primary vaccination with BNT162b2 were reported. A participant was considered a responder if at least one of the following conditions were satisfied: (1) If pre-booster 1 titer \<LLOQ, then post-booster titer \>=4\*LLOQ or (2) If pre-booster 1 titer \>LLOQ, then post-booster titer \>=4\*pre-booster value (titer).

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 original strain 2 weeks to 2 months after completing 2-dose primary vaccination with BNT162b2 were planned to be reported. A participant was considered a responder if at least one of the following conditions were satisfied: (1) If pre-dose 1 titer \<LLOQ, then post-vaccination titer \>=4\*LLOQ. (2) If pre-dose 1 titer \>LLOQ, then post-vaccination titer \>=4\*pre-dose 1 value (titer).

Time frame: 2 weeks to 2 months after primary vaccination with BNT162b2 (up to 1.5 months)

Population: Pre-dose data prior to primary vaccination with BNT162b2 was not collected and analyzed and thus the planned serological response data post-primary vaccination (BNT162b2) could not be estimated based on the protocol-defined serological response criteria.

Percentage of participants with seropositive response to vaccination against the SARS-CoV-2 leading variant of high consequence or concern (Delta) 2 weeks to 2 months after completing primary vaccination with 2-dose BNT162b2 were planned to be reported. A participant was considered a responder if one or both of the following conditions was satisfied: (1) Pre-dose titer \<LLOQ and post-vaccination titer \>=4\*LLOQ. or (2) Pre-dose titer \>LLOQ and post-vaccination titer \>=4\*pre-dose 1 titer value.

Time frame: 2 weeks to 2 months after primary vaccination with BNT162b2 (up to 1.5 months)

Population: NI analysis set included all vaccinated participants with post-baseline immunogenicity data without major protocol deviations and who were SARS-COV-2 seronegative at baseline (based on the serological test for SARS CoV-2-specific nucleocapsid antibodies \[N serology\]). Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against the leading variant of high consequence or concern (omicron variant) 14 days after Ad26.COV2.S booster vaccination were reported.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against the leading variant of high consequence or concern (omicron variant) 28 days after Ad26.COV2.S booster vaccination were reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

GMTs of neutralizing antibodies against the original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 14 days after Ad26.COV2.S booster vaccination were reported. GMT against original strain was assessed by VNA.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against the original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 28 days after Ad26.COV2.S booster vaccination were reported. GMT was assessed by VNA.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

Number of participants with antibodies binding to SARS-CoV-2 relevant variants of concern or individual SARS-CoV-2 Proteins by MSD were planned to be reported.

Time frame: From booster vaccination (Day 1) until 1 year from booster vaccination

Population: Data for this outcome measure was not collected and analyzed due to change in planned analysis.

Percentage of participants with antibodies binding to SARS-CoV-2 relevant variants of concern or individual SARS-CoV-2 Proteins by ELISA were planned to be reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population was analyzed. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure and 0 in the number analyzed field signifies that no participants were available for the analysis because data of antibodies binding to SARS-CoV-2 relevant variants of concern was not collected and analyzed due to change in planned analysis.

Percentage of participants with serological response against SARS-CoV-2 leading variant of high consequence or concern (omicron variant) 14 days after Ad26.COV2.S booster vaccination after primary vaccination with Ad26.COV2.S were reported.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 leading variant of high consequence or concern (omicron variant) 28 days after Ad26.COV2.S booster vaccination after primary vaccination with Ad26.COV2.S were reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 14 days after Ad26.COV2.S booster vaccination after primary vaccination with Ad26.COV2.S were reported. A participant was considered a responder if at least one of the following conditions were satisfied: (1) If pre-booster 1 titer \<LLOQ, then post-booster titer \>=4\*LLOQ or (2) If pre-booster 1 titer \>LLOQ, then post-booster titer \>=4\*pre-booster value (titer).

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: Per protocol immunogenicity (PPI) population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response against SARS-CoV-2 original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 28 days after Ad26.COV2.S booster vaccination after primary vaccination with Ad26.COV2.S were reported. A participant was considered a responder if at least one of the following conditions were satisfied: (1) If pre-booster 1 titer \<LLOQ, then post-booster titer \>=4\*LLOQ or (2) If pre-booster 1 titer \>LLOQ, then post-booster titer \>=4\*pre-booster value (titer).

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

Antibody GMTs of neutralizing antibodies against the leading variant of high consequence or concern (omicron variant) 14 days after Ad26.COV2.S booster vaccination after completing primary vaccination with BNT162b2 were reported.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Antibody GMTs of neutralizing antibodies against the original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 14 days after Ad26.COV2.S booster vaccination after completing primary vaccination with BNT162b2 were reported.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

GMTs of neutralizing antibodies against the leading variant of high consequence or concern (omicron variant) 28 days after Ad26.COV2.S booster vaccination after completing primary vaccination with BNT162b2 were reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

GMTs of neutralizing antibodies against the original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 28 days after Ad26.COV2.S booster vaccination after completing primary vaccination with BNT162b2 were reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

Number of participants with antibodies binding to SARS-CoV-2 relevant variants of concern or individual SARS-CoV- 2 proteins by MSD were planned to be reported.

Time frame: From booster vaccination (Day 1) until 1 year from booster vaccination

Population: Data for this outcome measure was not collected and analyzed due to change in planned analysis.

Percentage of participants with antibodies binding to SARS-CoV-2 relevant variants of concern or individual SARS-CoV- 2 proteins by ELISA were planned to be reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population was analyzed. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure and 0 in the number analyzed field signifies that no participants were available for the analysis because data of antibodies binding to SARS-CoV-2 relevant variants of concern was not collected and analyzed due to change in planned analysis.

Percentage of participants with serological response to vaccination against the leading variant of high consequence or concern (omicron variant) 14 days after Ad26.COV2.S booster vaccination after primary vaccination with BNT162b2 was reported.

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

Percentage of participants with serological response to vaccination against the leading variant of high consequence or concern (omicron variant) 28 days after Ad26.COV2.S booster vaccination after primary vaccination with BNT162b were reported.

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants with available data for this outcome measure.

Percentage of participants with serological response to vaccination against the original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (beta variant) 14 days after Ad26.COV2.S booster vaccination after primary vaccination with BNT162b2 were reported. A participant was considered a responder if at least one of the following conditions was satisfied: (1) If pre-booster 1 titer \<LLOQ, then post-booster titer \>=4\*LLOQ or (2) If pre-booster 1 titer \>LLOQ, then post-booster titer \>=4\*pre-booster value (titer).

Time frame: 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Percentage of participants with serological response to vaccination against the original strain, leading variant of high consequence or concern (delta variant), and other relevant variant of concern (Beta variant) 28 days after Ad26.COV2.S booster vaccination after primary vaccination with BNT162b2 were reported. A participant was considered a responder if at least one of the following conditions was satisfied: (1) If pre-booster 1 titer \<LLOQ, then post-booster titer \>=4\*LLOQ or (2) If pre-booster 1 titer \>LLOQ, then post-booster titer \>=4\*pre-booster value (titer).

Time frame: 28 days after Ad26.COV2.S booster vaccination (i.e., On Day 29)

Population: PPI population included all vaccinated participants for whom post-baseline immunogenicity data were available excluding participants with major protocol deviations expected to impact the immunogenicity outcomes. Here, N (Overall number of participants analyzed) signifies participants evaluable for this outcome measure.

Number of participants with AESIs were reported. AESIs are significant AEs that are judged to be of special interest because of clinical importance, known or suspected class effects, or based on nonclinical signals.

Time frame: From booster vaccination (Day 1) until 1 year post booster vaccination

Population: FAS included all participants with a documented study vaccine administration (Ad26.COV2.S).

Number of participants with antibodies binding to the SARS-CoV-2 nucleocapsid (N) protein at Day 1 as assessed by N-serology were planned to be reported.

Time frame: Day 1

Population: Data for this outcome measure was not collected and analyzed due to change in planned analysis.

SAE is any untoward medical occurrence that at any dose may result in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, is a suspected transmission of any infectious agent via a medicinal product.

Time frame: From booster vaccination (Day 1) until 1 year post booster vaccination

Population: FAS included all participants with a documented study vaccine administration (Ad26.COV2.S).

Participants who received the booster dose were asked to note the occurrence of injection site pain, erythema, and swelling at the study vaccine injection site in e-Diary daily for 7 days post-booster vaccination (day of vaccination and the subsequent 7 days).

Time frame: Up to 7 days after booster vaccination (Up to Day 8)

Population: Full analysis set (FAS) included all participants with a documented study vaccine administration (Ad26.COV2.S).

Participants recorded the temperature in the e-Diary in the evening of the day of vaccination, and then daily for the next 7 days approximately at the same time each day. If more than 1 measurement was made on any given day, the highest temperature of that day was recorded in the e-Diary. Fever was defined as endogenous elevation of body temperature \>= 38.0 degree Celsius or \>=100.4-degree Fahrenheit, as recorded in at least 1 measurement. Participants also noted the signs and symptoms in the e-Diary on a daily basis for 7 days post-booster vaccination (day of vaccination and the subsequent 7 days), if feasible, for the following events: fatigue, headache, nausea, myalgia.

Time frame: Up to 7 days after booster vaccination (Up to Day 8)

Population: FAS included all participants with a documented study vaccine administration (Ad26.COV2.S).

Unsolicited AEs were all AEs for which the participant was not specifically questioned in the participant diary.

Time frame: Up to 28 days after booster vaccination (Up to Day 29)

Population: FAS included all participants with a documented study vaccine administration (Ad26.COV2.S).