18 and older, any sex, with Coronavirus Disease. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Cohort 1: Percentage of Participants With Serological Response Against SARS-CoV-2 Original Strain 14 Days After Ad26.COV2.S Booster Vaccination After Completing Primary Vaccination With Ad26.COV2.SPrimary· 14 days after Ad26.COV2.S booster vaccination (i.e., on Day 15)
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.
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
63.4
57.7 – 68.9
Cohort 1: Ad26.COV2.S (2.5*10^10 vp)
57.9
52.1 – 63.6
Cohort 1: Ad26.COV2.S (1*10^10 vp)
64.5
53.9 – 74.2
Cohort 1: Geometric Mean Titers (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.SPrimary· 14 days after Ad26.COV2.S booster vaccination (i.e., on Day 15)
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).
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
1130
989 – 1291
Cohort 1: Ad26.COV2.S (2.5*10^10 vp)
915
792 – 1058
Cohort 1: Ad26.COV2.S (1*10^10 vp)
734
564 – 954
Cohort 1: Percentage of Participants With Serological Response Against SARS-CoV-2 Original Strain 28 Days After Primary Vaccination With Ad26.COV2.SPrimary· 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)
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.
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
15.4
11.6 – 19.9
Cohort 1: Ad26.COV2.S (2.5*10^10 vp)
16.8
12.9 – 21.4
Cohort 1: Ad26.COV2.S (1*10^10 vp)
11.7
6.4 – 19.2
Cohort 1: GMTs of Neutralizing Antibodies Against SARS-CoV-2 Original Strain 28 Days After Primary Vaccination With Ad26.COV2.SPrimary· 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)
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.
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
98
85 – 113
Cohort 1: Ad26.COV2.S (2.5*10^10 vp)
100
87 – 115
Cohort 1: Ad26.COV2.S (1*10^10 vp)
76
NA – 92
Cohort 1: Percentage of Participants With Serological Response Against the Delta Variant 14 Days After Ad26.COV2.S Booster Vaccination (5*10^10 vp Dose Level) After Completing Primary Vaccination With Ad26.COV2.SPrimary· 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)
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 anal
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
56.7
50.9 – 62.4
Cohort 1: GMTs of Neutralizing Antibodies Against the 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.SPrimary· 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)
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.
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
471
411 – 539
Cohort 1: 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.SPrimary· 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)
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\*1
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
8.8
5.9 – 12.5
Cohort 1: 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)Primary· 28 days after primary vaccination with Ad26.COV2.S (Day 29 of study VAC31518COV3001)
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.
Group
Value
95% CI
Cohort 1: Ad26.COV2.S (5*10^10 vp)
NA
NA – NA
Cohort 2: 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 BNT162b2Primary· 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)
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).
Group
Value
95% CI
Cohort 2: Ad26.COV2.S (5*10^10 vp)
97.0
94.3 – 98.6
Cohort 2: Ad26.COV2.S (2.5*10^10 vp)
90.5
86.5 – 93.6
Cohort 2: Ad26.COV2.S (1*10^10 vp)
89.8
81.5 – 95.2
Cohort 2: 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 BNT162b2Primary· 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)
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.
Group
Value
95% CI
Cohort 2: Ad26.COV2.S (5*10^10 vp)
4439
4027 – 4893
Cohort 2: Ad26.COV2.S (2.5*10^10 vp)
3566
3212 – 3958
Cohort 2: Ad26.COV2.S (1*10^10 vp)
3218
2582 – 4010
Cohort 2: GMTs of Neutralizing Antibodies Against SARS-CoV-2 Original Strain 2 Weeks to 2 Months After Completing 2-dose Primary Vaccination With BNT162b2 (Pfizer BNT162b2 External Samples)Primary· 2 weeks to 2 months after primary vaccination with BNT162b2 (up to 1.5 months)
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.
Group
Value
95% CI
Pfizer External Samples
1281
1086 – 1510
Cohort 2: Percentage of Participants With Serological Response Against SARS-CoV-2 Delta Variant 14 Days After Booster Vaccination (5*10^10 vp Dose Level) After Completing 2-dose Primary Vaccination With BNT162b2Primary· 14 days after Ad26.COV2.S booster vaccination (i.e., On Day 15)
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 collect
Group
Value
95% CI
Cohort 2: Ad26.COV2.S (5*10^10 vp)
93.6
90.2 – 96.1
Adverse events — posted to ClinicalTrials.gov
Time frame: From booster vaccination (Day 1) until 1 year post booster vaccination.
Reporting threshold: 2%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
The purposes of this study are to demonstrate the non-inferiority (NI) of the neutralizing antibody response to the original strain 14 days after booster vaccination with Ad26.COV2.S at the different dose levels, administered greater than or equal to (\>=) 6 months after single-dose primary vaccination with Ad26.COV2.S, compared to the neutralizing antibody response to the original strain induced by single-dose primary vaccination with Ad26.COV2.S; To demonstrate the NI of the neutralizing antibody response to the leading variant of high consequence or concern 14 days after booster vaccination with Ad26.COV2.S at the 5\*10\^10 virus particle (vp) dose level, administered \>= 6 months after single-dose primary vaccination with Ad26.COV2.S (5\*10\^10 vp dose level), compared to the neutralizing antibody response to the leading variant of high consequence or concern induced by single-dose primary vaccination with Ad26.COV2.S at the 5\*10\^10 vp dose level, if feasible; To demonstrate the NI of the neutralizing antibody response to the original strain 14 days after booster vaccination with Ad26.COV2.S at the different dose levels administered \>=6 months after completing a 2-dose primary vaccination with Pfizer BNT162b2, compared to the neutralizing antibody response to the original strain induced by 2-dose primary vaccination with Pfizer BNT162b2; To demonstrate the NI of neutralizing antibody response to the leading variant of high consequence or concern 14 days after booster vaccination with Ad26.COV2.S at the 5\*10\^10 vp dose level, administered \>= 6 months after completing a 2-dose primary vaccination with Pfizer BNT162b2, compared to the neutralizing antibody response to the leading variant of high consequence or concern induced by 2-dose primary vaccination with Pfizer BNT162b2, if feasible.
Publications & conference data
4 peer-reviewed publications reference this trial (live from Europe PMC):
NCT04908722 — A Study to Evaluate Dose Levels of Ad26.COV2.S Administered as a Two-dose Schedule in Healthy Adults
· Phase 3
· completed
Other Janssen Vaccines & Prevention B.V. trials
Trials by the same sponsor.
NCT05901636 — A Clinical Study to Evaluate an Experimental Universal Influenza Vaccine, INFLUENZA G1 mHA, in Healthy Adults
· Phase 1, PHASE2
· completed
NCT05327816 — A Study of Various Respiratory Syncytial Virus (RSV) Pre-Fusion (preF)-Based Vaccine Formulations in Adults Aged 60 Year
· Phase 1, PHASE2
· terminated
NCT05091307 — A Study of Ad26.COV2.S and Influenza Vaccines in Healthy Adults
· Phase 3
· completed
NCT05101486 — A Study of an Ad26.RSV.PreF-based Regimen at the End of Shelf-life in Adults Aged 60 to 75 Years
· Phase 3
· completed
NCT05083585 — A Study Evaluating the Immunogenicity of Different Clinical Trial Materials of Ad26.RSV.preF- Based Vaccine in Adults Ag
· Phase 3
· completed
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Janssen Vaccines & Prevention B.V.
Last refreshed: 4 February 2025
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT04999111.