Trial · NCT06279871

Immunogenicity and Safety Study of Self-amplifying mRNA COVID-19 Vaccine Administered With Influenza Vaccines in Adults

NCT06279871, Phase 3, Completed, Arcturus Therapeutics, Inc.; results first posted 2025-12-12

3 sourcestrials-2026-11-12-0.5.0

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ConductScience Library. Immunogenicity and Safety Study of Self-amplifying mRNA COVID-19 Vaccine Administered With Influenza Vaccines in Adults. Trials, record NCT06279871. Release trials-2026-11-12-0.5.0, 12 Nov 2026. https://conductscience.org/library/trials/NCT06279871

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Trial

As registered on ClinicalTrials.gov, in the graph's capture of the registry.

Title: Immunogenicity and Safety Study of Self-amplifying mRNA COVID-19 Vaccine Administered With Influenza Vaccines in Adults
NCT number: NCT06279871
Status: Completed
Phases: Phase 3
Enrollment: 1,514 participants, actual
Lead sponsor: Arcturus Therapeutics, Inc.
Conditions: COVID-19
Interventions: ARCT-2303, Influenza vaccine, Influenza vaccine, adjuvanted, Placebo
First posted: 2024-02-28
Last updated: 2025-12-12
Results first posted: 2025-12-12

Source ClinicalTrials.gov

Registered outcomes23

Each outcome the trial registered, primary first, in ClinicalTrials.gov's words.

List	Outcome	Time frame	Description
Primary	Groups 2a and 2b and ARCT-154-J01 Historical Control: Geometric Mean Titers (GMT) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody Titers Against Omicron XBB.1.5 Subvariant at Day 29	Day 29
Primary	Groups 2a and 2b and ARCT-154-J01 Historical Control: Number of Participants With Seroconversion to SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	Day 29	Seroconversion was defined as either a pre-vaccination titer below the lower limit of quantitation (LLOQ) and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer.
Primary	Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Day 29	Influenza vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.
Primary	Groups 1a and 2a: Adjusted GMTs of SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	Day 29
Secondary	Groups 1a and 2a: GMT of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Days 1, 29 and 181	Group 1a: Days 1 and 29; Group 2a: Days 1, 29, and 181
Secondary	Groups 1a and 2a: Geometric Mean Fold Rise (GMFR) of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Days 29 and 181	Group 1a: Day 29; Group 2a: Days 29 and 181	GMFR is reported as a ratio to Day 1.
Secondary	Groups 1a and 2a: Number of Participants With Seroconversion of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Day 29	Day 29	Seroconversion was defined as either a pre-vaccination titer below the LLOQ and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer.
Secondary	Groups 1a and 2a: Number of Participants With SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant Titer ≥ LLOQ at Days 1 and 29	Days 1 and 29
Secondary	Groups 1a and 3a: GMTs of HI Assay Titers Against Influenza Vaccine Strains at Days 1 and 29	Days 1 and 29	Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.
Secondary	Groups 1a and 3a: GMFR of HI Assay Titers Against Influenza Vaccine Strains at Day 29	Day 29	Vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata. GMFR is reported as a ratio to Day 1.

1 to 10 of 23Source ClinicalTrials.gov

See all 23 registered outcomes

Outcomes23

Each outcome the trial posted results for, in ClinicalTrials.gov's words.

Type	Outcome	Time frame	Population	Units	Measured as
PRIMARY	Groups 2a and 2b and ARCT-154-J01 Historical Control: Geometric Mean Titers (GMT) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody Titers Against Omicron XBB.1.5 Subvariant at Day 29	Day 29	Study treatment arm: per protocol (PP) set for immunogenicity, participants in the Modified Intent-To-Treat Analysis Set (mITT) who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. As pre-specified, data for groups 2a \& 2b were collected and are reported pooled as a combined group.	Titer	GEOMETRIC_MEAN
PRIMARY	Groups 2a and 2b and ARCT-154-J01 Historical Control: Number of Participants With Seroconversion to SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	Day 29	Study treatment arm: PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. As pre-specified, data for groups 2a \&2b were collected and are reported pooled as a combined group.	Participants	COUNT_OF_PARTICIPANTS
PRIMARY	Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Day 29	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.	titers	GEOMETRIC_MEAN
PRIMARY	Groups 1a and 2a: Adjusted GMTs of SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	Day 29	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.	titers	GEOMETRIC_MEAN
SECONDARY	Groups 1a and 2a: GMT of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Days 1, 29 and 181	Group 1a: Days 1 and 29; Group 2a: Days 1, 29, and 181	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. Overall number of participants analyzed = participants evaluable for this outcome measure. Number analyzed = participants evaluable at the specified timepoint.	titers	GEOMETRIC_MEAN
SECONDARY	Groups 1a and 2a: Geometric Mean Fold Rise (GMFR) of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Days 29 and 181	Group 1a: Day 29; Group 2a: Days 29 and 181	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29 or Day 181) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data. Overall number of participants analyzed = participants evaluable for this outcome measure. Number analyzed = participants evaluable at the specified timepoint.	ratio	GEOMETRIC_MEAN
SECONDARY	Groups 1a and 2a: Number of Participants With Seroconversion of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Day 29	Day 29	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.	Participants	COUNT_OF_PARTICIPANTS
SECONDARY	Groups 1a and 2a: Number of Participants With SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant Titer ≥ LLOQ at Days 1 and 29	Days 1 and 29	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.	Participants	COUNT_OF_PARTICIPANTS
SECONDARY	Groups 1a and 3a: GMTs of HI Assay Titers Against Influenza Vaccine Strains at Days 1 and 29	Days 1 and 29	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.	titer	GEOMETRIC_MEAN
SECONDARY	Groups 1a and 3a: GMFR of HI Assay Titers Against Influenza Vaccine Strains at Day 29	Day 29	PP set for immunogenicity, which included participants in the mITT who correctly received all protocol-required doses of study vaccines at Day 1 and who at or prior to the specified timepoint (Day 29) had no evidence of SARS-CoV-2 infection and no protocol deviations impacting the analysis of immunogenicity data.	ratio	GEOMETRIC_MEAN

1 to 10 of 23Source ClinicalTrials.gov

See all 23 outcomes

Results by group198

Each measurement the trial posted, group by group, in the words and numbers it posted.

Outcome	Group	Category	Value	Spread	Units
Groups 2a and 2b and ARCT-154-J01 Historical Control: Geometric Mean Titers (GMT) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody Titers Against Omicron XBB.1.5 Subvariant at Day 29	Cohort A Group 2a: ARCT-2303 + Placebo + QIV and Cohort B Group 2b: ARCT-2303 + Placebo + aQIV		718	95% Confidence Interval 652 to 791	Titer
Groups 2a and 2b and ARCT-154-J01 Historical Control: Geometric Mean Titers (GMT) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody Titers Against Omicron XBB.1.5 Subvariant at Day 29	ARCT-154-J01 (Historical Control)		263	95% Confidence Interval 236 to 293	Titer
Groups 2a and 2b and ARCT-154-J01 Historical Control: Number of Participants With Seroconversion to SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	Cohort A Group 2a: ARCT-2303 + Placebo + QIV and Cohort B Group 2b: ARCT-2303 + Placebo + aQIV		349		Participants
Groups 2a and 2b and ARCT-154-J01 Historical Control: Number of Participants With Seroconversion to SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	ARCT-154-J01 (Historical Control)		175		Participants
Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	A/H1N1	338	95% Confidence Interval 289 to 395	titers
Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Cohort A Group 3a: QIV + Placebo + ARCT-2303	A/H1N1	354	95% Confidence Interval 304 to 413	titers
Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	A/H3N2	280	95% Confidence Interval 242 to 325	titers
Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Cohort A Group 3a: QIV + Placebo + ARCT-2303	A/H3N2	269	95% Confidence Interval 232 to 311	titers
Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	B/Victoria	109	95% Confidence Interval 92 to 129	titers
Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29	Cohort A Group 3a: QIV + Placebo + ARCT-2303	B/Victoria	99	95% Confidence Interval 84 to 117	titers

1 to 10 of 198Source ClinicalTrials.gov

See all 198 results by group

Participant flow35

How many started, completed or left each group, period by period.

Period	Milestone	Group	Participants
Overall Study	STARTED	Cohort A Group 1a: ARCT-2303+ Quadrivalent Influenza Vaccine (QIV) + Placebo	408
Overall Study	STARTED	Cohort A Group 2a: ARCT-2303 + Placebo + QIV	406
Overall Study	STARTED	Cohort A Group 3a: QIV + Placebo + ARCT-2303	405
Overall Study	STARTED	Cohort B Group 1b: ARCT-2303 + Adjuvanted QIV (aQIV) + Placebo	99
Overall Study	STARTED	Cohort B Group 2b: ARCT-2303 + Placebo + aQIV	98
Overall Study	STARTED	Cohort B Group 3b: aQIV + Placebo + ARCT-2303	98
Overall Study	STARTED	ARCT-154-J01 (Historical Control)	385
Overall Study	Received Dose 1	Cohort A Group 1a: ARCT-2303+ Quadrivalent Influenza Vaccine (QIV) + Placebo	403
Overall Study	Received Dose 1	Cohort A Group 2a: ARCT-2303 + Placebo + QIV	403
Overall Study	Received Dose 1	Cohort A Group 3a: QIV + Placebo + ARCT-2303	398

1 to 10 of 35Source ClinicalTrials.gov

See all 35 participant flow

Adverse events228

Each adverse event the trial posted, group by group: the participants affected out of those at risk.

Type	Event	Organ system	Group	Affected	At risk
other	Diarrhoea	Gastrointestinal disorders	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	0	403
other	Diarrhoea	Gastrointestinal disorders	Cohort A Group 2a: ARCT-2303 + Placebo + QIV	0	403
other	Diarrhoea	Gastrointestinal disorders	Cohort A Group 3a: QIV + Placebo + ARCT-2303	0	398
other	Diarrhoea	Gastrointestinal disorders	Cohort B Group 1b: ARCT-2303 + Adjuvanted QIV (aQIV) + Placebo	0	99
other	Diarrhoea	Gastrointestinal disorders	Cohort B Group 2b: ARCT-2303 + Placebo + aQIV	0	98
other	Diarrhoea	Gastrointestinal disorders	Cohort B Group 3b: aQIV + Placebo + ARCT-2303	3	98
other	COVID-19	Infections and infestations	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	22	403
other	COVID-19	Infections and infestations	Cohort A Group 2a: ARCT-2303 + Placebo + QIV	21	403
other	COVID-19	Infections and infestations	Cohort A Group 3a: QIV + Placebo + ARCT-2303	18	398
other	COVID-19	Infections and infestations	Cohort B Group 1b: ARCT-2303 + Adjuvanted QIV (aQIV) + Placebo	3	99

1 to 10 of 228Source ClinicalTrials.gov

See all 228 adverse events

Adverse event totals18

The totals the trial posted for each group.

Total	Group	Affected	At risk
Total, all-cause mortality	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	0	403
Total, all-cause mortality	Cohort A Group 2a: ARCT-2303 + Placebo + QIV	0	403
Total, all-cause mortality	Cohort A Group 3a: QIV + Placebo + ARCT-2303	0	398
Total, all-cause mortality	Cohort B Group 1b: ARCT-2303 + Adjuvanted QIV (aQIV) + Placebo	0	99
Total, all-cause mortality	Cohort B Group 2b: ARCT-2303 + Placebo + aQIV	0	98
Total, all-cause mortality	Cohort B Group 3b: aQIV + Placebo + ARCT-2303	1	98
Total, other adverse events	Cohort A Group 1a: ARCT-2303+ QIV + Placebo	65	403
Total, other adverse events	Cohort A Group 2a: ARCT-2303 + Placebo + QIV	59	403
Total, other adverse events	Cohort A Group 3a: QIV + Placebo + ARCT-2303	49	398
Total, other adverse events	Cohort B Group 1b: ARCT-2303 + Adjuvanted QIV (aQIV) + Placebo	6	99

1 to 10 of 18Source ClinicalTrials.gov

See all 18 adverse event totals

Papers1

The papers the trial lists on ClinicalTrials.gov.

PMID	Listed as
40896462	DERIVED

Source PubMed

Grants0

The grants NIH RePORTER links to the trial, newest funded first: NIH's, and some of AHRQ's, CDC's, FDA's and VA's. Each shows its title, principal investigators, organization and funder in its newest year.

None in this release.

Trial comparisons3

Comparisons of the trial's two groups, calculated by ConductScience from the counts it posted.

Comparison	Source
Cohort A Group 1a: ARCT-2303+ QIV + Placebo vs Cohort A Group 2a: ARCT-2303 + Placebo + QIV: Groups 1a and 2a: Number of Participants With Seroconversion of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Day 29	Trial comparisons
Cohort B Group 1b: ARCT-2303 + Adjuvanted QIV (aQIV) + Placebo vs Cohort B Group 2b: ARCT-2303 + Placebo + aQIV: Groups 1b and 2b: Number of Participants With Seroconversion of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Day 29	Trial comparisons
Cohort A Group 2a: ARCT-2303 + Placebo + QIV and Cohort B Group 2b: ARCT-2303 + Placebo + aQIV vs ARCT-154-J01 (Historical Control): Groups 2a and 2b and ARCT-154-J01 Historical Control: Number of Participants With Seroconversion to SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29	Trial comparisons

Tests0

The ConductCognition tests this trial's registered outcomes name, as ScienceGraph matched them in trial-tests-2026-11-12-0.2.1.

None in this release.

Data dates

The day each source was copied for this release.

ClinicalTrials.gov: 2026-11-12; ClinicalTrials.gov
Results, from AACT: 2026-03-23; AACT
NIH grant links: 2026-11-13; NIH RePORTER

Sources 3

ClinicalTrials.gov's posted results, through CTTI's AACTFreely available. Acknowledgement requested
ClinicalTrials.govNo license stated
NIH RePORTER's clinical studies and project filesPublic domain

Each source's terms

ClinicalTrials.gov's posted results, through CTTI's AACTClinicalTrials.gov data via Aggregate Analysis of ClinicalTrials.gov (AACT), CTTI. CTTI makes its materials freely available and requests acknowledgement. https://aact.ctti-clinicaltrials.org/documentation/299
ClinicalTrials.govnone stated
NIH RePORTER's clinical studies and project filesPublic domain (NIH RePORTER)

ClinicalTrials.gov's data carry an international copyright outside the United States: https://clinicaltrials.gov/about-site/terms-conditions.

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Read this trial from software.

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