COVID-19 PreventionPhase 2HORIZON 1NCT04765384

A Study of Ad26.COV2.S in Healthy Pregnant Participants (COVID-19)

A Phase 2 study testing Ad26.COV2.S in people with COVID-19 Prevention, run by Janssen Vaccines & Prevention B.V. at 18 sites in 3 countries.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record

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Trial summary

The purpose of this study is to assess the safety and reactogenicity of Ad26.COV2.S administered intramuscularly (IM) as a 1-dose schedule at the standard dose level in adult participants during the second and/or third trimester of pregnancy and (potentially) post-partum; to assess the humoral immune response in… Read more about this study

Who is it for?: Ages 18 to 45 years, women onlyHealthy volunteers can take part
Conditions the study is for: COVID-19 Prevention
What is being tested?: Ad26.COV2.S
Type of treatment: Vaccines, Injection or infusion
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 51 participants
Where: 18 sitesin 3 countries
Study dates: 27 Aug 2021to 24 Nov 2023
Phase: Phase 2
Are there results?: Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 18 to 45 years
Women only
Healthy volunteers accepted
Adult

Who may be able to join

If on medication for a condition, the medication dose must have been stable for at least 4 weeks preceding vaccination
Participant must be healthy as confirmed by medical history, physical examination, vital signs, and obstetric history performed at Screening. Participant may have underlying illnesses, as long as the symptoms and signs are medically controlled
Participant will be at second or third trimester of pregnancy, that is, Week 16 to Week 38 of gestation (inclusive), at the time of vaccination, based on ultrasound at the time of screening (or not longer than 10 days prior to vaccination if performed elsewhere)
Participant agrees to not donate bone marrow, blood, and blood products from the first study vaccine administration until 3 months after receiving the last dose of study vaccine
Participant must be willing to provide verifiable identification, has means to be contacted and to contact the investigator during the study
Participant either received their last COVID-19 vaccination with an authorized/licensed COVID-19 vaccine (at least 4 months prior to first study vaccination) or is COVID 19 vaccine-naïve

Who cannot join

Participants with medical or obstetric histories that put them at higher risk for maternal or fetal complications (example, chronic pregnancy-related disorders, birth defects or genetic conditions during previous pregnancy)
Participant with abnormal pregnancy screening test (example, ultrasound fetal abnormalities, maternal blood screen)
Participant has a history of malignancy within 2 years before screening (exceptions are squamous, basal cell carcinomas of the skin, carcinoma in situ of the cervix, or malignancy, considered cured with minimal risk of recurrence)
Participant has a known or suspected allergy or history of anaphylaxis or other serious adverse reactions to vaccines or their excipients (including specifically the excipients of the study vaccine)
Participant has a history of any serious, chronic, or progressive neurological disorders or seizures including Guillain-Barre syndrome, with the exception of febrile seizures during childhood
Participant has a positive diagnostic test result (polymerase chain reaction [PCR] based viral ribonucleic acid [RNA] detection) severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection at screening or Day 1 (if more than 4 days in between)
Participant has a history of thrombosis with thrombocytopenia syndrome (TTS), including cerebral venous sinus thrombosis (CVST), or heparin-induced thrombocytopenia (HIT)
Participant has a history of capillary leak syndrome (CLS)

Trial locations and contacts

18 sites in 3 countries.

Country

City, postcode or hospital

18 sites in 3 countries

Brazil10 sites

Universidade Federal De Minas Gerais - Hospital das Clínicas
Belo Horizonte, 30130-100
Sociedade Literaria e Caritativa Santo Agostinho Hospital Sao Jose
Criciúma, 88811-508
Associacaode Ensino de Marilia LTDA - UNIMAR - Universidade de Marilia
Marília, 17525-160
Centro de Estudos e Pesquisas em Moléstias Infecciosas - CEPCLIN
Natal, 59025-050
Hospital das Clinicas de Porto Alegre
Porto Alegre, 90035-903
NPCRS Nucleo de Pesquisa Clinica do Rio Grande do Sul
Porto Alegre, 90430-001
CEMEC - Centro Multidisciplinar de Estudos Clínicos
São Bernardo do Campo, 09715-090
Fundacao Faculdade Regional de Medicina de Sao Jose do Rio Preto Hospital de Base
São José do Rio Preto, 15090-000
Clinical Research College
São Paulo, 4534002
CMPC - Consultoria Médica e Pesquisa Clínica
Sorocaba, 18040-425

Other trials in Brazil

United States4 sites

Medpharmics, LLC
Albuquerque, New Mexico, 87102
Medpharmics, LLC
Gulfport, Mississippi, 39503
Maximos OB/GYN
League City, Texas, 77573
Meridian Clinical Research, LLC
Norfolk, Nebraska, 68701

Other trials in United States

South Africa4 sites

Ndlovu Elandsdoorn Site
Dennilton, 0485
Shandukani Research Centre
Johannesburg, 2001
Stanza Clinical Research Centre : Mamelodi
Mamelodi East, 0122
Perinatal HIV Research Unit, Chris Hani Baragwanath Hospital
Soweto, 1864

Other trials in South Africa

About this study

Official title: An Open-label, Phase 2 Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of Ad26.COV2.S in Healthy Pregnant Participants

Read the detailed description

There is an increased risk of severe coronavirus disease-2019 (COVID-19) during pregnancy, as well as an increased risk of adverse birth outcomes. Therefore, the aim of this study is to assess the safety, reactogenicity and immunogenicity of Ad26.COV2.S in adult participants in the second and/or third trimester of pregnancy. Ad26.COV2.S (also known as Ad26COVS1) is a monovalent vaccine composed of a recombinant, replication incompetent adenovirus type 26 (Ad26) vector, constructed to encode the S protein derived from a severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) clinical isolate, stabilized in its prefusion conformation. For each adult participant, the total study duration from screening until the last follow-up visit will be approximately 16 months. The study will consist of a screening phase (28 days), vaccination period (study period from vaccination to pregnancy completion/termination) and a follow-up period (up to 12 months post pregnancy completion/termination). For neonates/infants born to the participants in the study will be followed for approximately 12 months postpartum. Safety assessments will include immunogenicity assessments, physical examination, vital signs, clinical safety laboratory assessments, medical, obstetric and delivery history, pregnancy outcome, neonate safety assessment, adverse events (AEs), serious adverse events (SAEs), and adverse events of special interest (AESI).

Conditions: COVID-19 Prevention
Being tested: Ad26.COV2.S

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

Ad26.COV2.SBiological
Also called JNJ-78436735, Ad26COVS1
Participants will receive intramuscular (IM) injection of Ad26.COV2.S.

Study groups in NCT04765384
Study group	Role	What they receive
Groups 1-4: Ad26.COV2.S (One Dose)	Experimental	Participants who are previously vaccinated (Group 1-3) and participants who are vaccine naïve (Group 4) will receive single dose of Ad26.COV2.S vaccine at standard dose level on Day 1. Participants from group 4 who are no longer pregnant may receive single booster dose of Ad26.COV2.S vaccine at standard dose level. Receives: Biological: Ad26.COV2.S

What is being measured

The primary outcome is the main question the study is designed to answer.

Number of Adult Participants With Solicited Local Adverse Events (AEs) for 7 Days Post First Vaccination
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.
Measured: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8)
Number of Adult Participants With Solicited Systemic AEs for 7 Days Post First Vaccination
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.
Measured: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8)
Number of Adult Participants With Unsolicited AEs for 28 Days Post First Vaccination
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.
Measured: From first vaccination on Day 1 up to 28 days post first vaccination (up to Day 29)
Number of Adult Participants With Serious Adverse Events (SAEs) From First Vaccination Until End of the Study (EOS)
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.
Measured: From first vaccination on Day 1 until end of study (up to post-partum [PP] Day 366 [Day 15 up to Day 554])
Number of Adult Participants With Adverse Events of Special Interest (AESIs) From First Vaccination Until EOS
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.
Measured: From first vaccination on Day 1 until end of study (up to PP Day 366 [Day 15 up to Day 554])
Number of Adult Participants With Medically Attended Adverse Events (MAAEs) Until 6 Months Post First Vaccination
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.
Measured: From first vaccination on Day 1 until 6 months post first vaccination (up to Day 183)
Number of Adult Participants With AEs Leading to Study Discontinuation
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.
Measured: From first vaccination on Day 1 until end of study (up to PP Day 366 [Day 15 up to Day 554])
Serological Response to Vaccination as Measured by S-Enzyme-linked Immunosorbent Assay (S-ELISA) in Adult Participants 28 Days Post First Vaccination
Serological response to vaccination as measured by S-ELISA in adult participants 28 days post first vaccination was reported.
Measured: 28 days post first vaccination on Day 1 (at Day 29)

Secondary outcomes (20)

Group 4: Number of Adult Participants With Solicited Local AEs for 7 Days Post Booster Vaccination
Number of adult participants with solicited local AEs for 7 days post booster 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 booster vaccination (day of booster vaccination and the subsequent 7 days). Solicited local AEs are: injection site pain/tenderness, erythema, swelling at the vaccination site.
Measured: 7 days post booster vaccination (Day 84 up to Day 371)
Group 4: Number of Adult Participants With Solicited Systemic AEs for 7 Days Post Booster Vaccination
Number of adult participants with solicited systemic AEs for 7 days post booster 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 booster vaccination. Participants were instructed on how to note signs and symptoms in the diary on a daily basis for 7 days post-vaccination (day of booster vaccination and the subsequent 7 days) for the following solicited systemic AEs: fatigue, headache, nausea, myalgia.
Measured: 7 days post booster vaccination (Day 84 up to Day 371)
Group 4: Number of Adult Participants With Unsolicited AEs for 28 Days Post Booster Vaccination
Number of adult participants with unsolicited AEs for 28 days post booster 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.
Measured: 28 days post booster vaccination (Day 84 up to Day 392)
Group 4: Number of Adult Participants With SAEs Post Booster Vaccination Until EOS
Number of adult participants with SAEs post booster vaccination until EOS were reported. 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. SAE 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.
Measured: From booster vaccination (Day 84 up to Day 364) until EOS (up to PP Day 366 [Day 366 up to Day 554])
Group 4: Number of Adult Participants With AESIs Post Booster Vaccination Until EOS
Number of adult participants with AESI post booster 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.
Measured: From booster vaccination (Day 84 up to Day 364) until EOS (up to PP Day 366 [Day 366 up to Day 554])
Group 4: Number of Adult Participants With MAAEs Until 6 Months Post Booster Vaccination
Number of adult participants with MAAEs until 6 months post booster vaccination were 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.
Measured: 6 months post booster vaccination (Day 84 up to Day 546)
Group 4: Number of Adult Participants With AEs Leading to Study Discontinuation Post Booster Vaccination Until EOS
Number of adult participants with AEs leading to study discontinuation post booster 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. All AEs leading to discontinuation from the study (regardless of the causal relationship) were reported for all adult participants from the moment of booster vaccination until completion of the participant's last study-related procedure.
Measured: From post booster vaccination (Day 84 up to Day 364) until EOS (up to PP Day 366 [Day 366 up to Day 554])
Number of Adult Participants With Pregnancy Outcomes
Number of adult participants with pregnancy outcomes were reported. Pregnancy outcomes in adult participants included live term birth, live preterm birth, stillbirth, and abortion.
Measured: From first vaccination on Day 1 until PP Day 1 (Day 7 up to Day 163)
Number of Adult Participants With Pregnancy Related AEs Throughout Pregnancy
Number of adult participants with pregnancy related AEs throughout pregnancy were reported. Pregnancy related AEs in adult participants were collected based on 2 baseline gestational age groups (adult participants who received vaccination at 16 to 27 weeks [>=16 weeks to <28 weeks] and at 28 to 38 weeks [>=28 weeks to <=38 weeks]) and included gestational hypertension, foetal growth restriction, haemorrhage in pregnancy, polyhydramnios, pre-eclampsia, premature rupture of membranes, preterm premature rupture of membranes, bradycardia foetal, premature baby, amniorrhexis, foetalgrowth restriction, amniotic fluid volume decreased.
Measured: From first vaccination on Day 1 until PP Day 1 (Day 7 up to Day 163)
Serological Response to First Vaccination as Measured by S-ELISA in Adult Participants at All Blood Collection Timepoints Post First Vaccination
Serological response to first vaccination as measured by S-ELISA at all blood collection timepoints post first vaccination were reported.
Measured: Day 1, Day 29, PP Day 1 (Day 7 up to Day 163), PP Day 183 (Day 189 up to Day 345)
Serological Response to First Vaccination as Measured by Virus Neutralization Assay (VNA) Titers, 28 Days in Adult Participants Post First Vaccination
Serological response to first vaccination measured by VNA titers at 28 days in adult participants post first vaccination was reported. Data were expressed as 50 percent (%) inhibitory concentration (IC50) units.
Measured: 28 days post first vaccination on Day 1 (at Day 29)
Group 4: Serological Response to Booster Vaccination Measured by Binding (S-ELISA) Antibody Titers in Adult Participants at Blood Collection Time Points Post Booster Vaccination
Serological response to vaccination as measured by binding (S-ELISA) antibody titers in adult participants at blood collection time points post booster vaccination were reported.
Measured: Booster Day 1 (Day 84 up to Day 364), Booster Day 29 (Day 112 up to Day 392)
Group 4: Serological Response to Booster Vaccination Measured by Neutralizing (VNA) Antibody Titers in Adult Participants at Blood Collection Time Points Post Booster Vaccination
Serological response to booster vaccination measured by neutralizing VNA antibody titers in adult participants at blood collection time points post booster vaccination were reported. Data were expressed as IC50 units.
Measured: Booster Day 1 (Day 84 up to Day 364), Booster Day 29 (Day 112 up to Day 392)
Serological Response to Vaccination as Measured by S-ELISA at Birth (That is, in Cord Blood) and at 2 Months and 6 Months of Age in Neonates and Infants Born to Adult Participants
Serological response to vaccination as measured by S-ELISA at birth (that is, in cord blood) and at 2 months and 6 months of age in neonates and infants born to adult participants were reported.
Measured: At birth (postnatal [PN] Day 1 [Day 7 up to Day 163]), 2 months (up to PN Day 61 [Day 67 up to Day 223]) and 6 months (up to PN Day 183 [Day 189 up to Day 345])
Serological Response to Vaccination as Measured by VNA Titers at Birth (That is, in Cord Blood) in Neonates and Infants Born to Adult Participants
Serological response to vaccination as measured by VNA titers at birth (that is, in cord blood) in neonates and infants born to adult participants were reported. Data were expressed as IC50 units.
Measured: At Birth (PN Day 1 [Day 7 up to Day 163])
Number of Neonates and Infants With SAEs (Including MIS-C) From Birth Up to 12 Months of Age in Neonates and Infants Born to Adult Participants
An AE is any untoward medical occurrence in participants in the study that does not necessarily have a causal relationship with pharmaceutical/biological agent under study. SAE: any untoward medical occurrence that resulted in 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. MIS-C: a serious and potentially fatal condition in infants and children with SARS-CoV-2, which resulted in inflammation involving multiple organs. Symptoms of MIS-C: persistent fever, fatigue and signs and symptoms including multiorgan systems (cardiac, gastrointestinal, renal, hematologic, dermatologic, neurologic) involvement, elevated inflammatory markers and, in severe cases, hypotension and shock.
Measured: From birth (PN Day 1 [Day 7 up to Day 163]) up to 12 months of age (up to PN Day 366 [Day 372 up to Day 528])
Number of Neonates and Infants With AESIs From Birth Until 12 Months of Age in Neonates and Infants Born to Adult Participants
Number of neonates and infants with AESIs from birth until 12 months of age in neonates and infants born to adult participants were reported. TTS is a syndrome characterized by a combination of both a thrombotic event and thrombocytopenia.
Measured: From birth (PN Day 1 [Day 7 up to Day 163]) until 12 months of age (up to PN Day 366 [Day 372 up to Day 528])
Number of Neonates and Infants With MAAEs From Birth Until 6 Months of Age in Neonates and Infants Born to Adult Participants
Number of neonates and infants with MAAEs from birth until 6 months of age in neonates and infants born to adult participants were 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 were collected as part of the MAAEs.
Measured: From birth (PN Day 1 [Day 7 up to Day 163]) until 6 months of age (up to PN 183 [Day 189 up to Day 345])
Number of Neonates and Infants With AEs Leading to Study Discontinuation From Birth Until Study Discontinuation
Number of neonates and infants with AEs leading to study discontinuation from birth until study discontinuation were reported. An AE is any untoward medical occurrence in participants who does not necessarily have a causal relationship with pharmaceutical/biological agent under study. All AEs leading to discontinuation from the study (regardless of the causal relationship) were reported for all neonates and infants.
Measured: From birth (PN Day 1 [Day 7 up to Day 163]) until study discontinuation (until 12 months of age [up to PN Day 366 {Day 372 up to Day 528}])
Number of Neonates and Infants With Different Birth Outcomes From Birth Up to 12 Months of Age
Number of neonates and infants with different birth outcomes from birth until 12 months of age were reported. Neonate/infant outcomes included normal neonate, term neonate with (or without) complications, preterm neonate with (or without) complications, neonatal infection, respiratory distress, congenital anomalies, neonatal death, low birth weight, and small for gestational age.
Measured: From birth (PN Day 1 [Day 7 up to Day 163]) up to 12 months of age (up to PN Day 366 [Day 372 up to Day 528])

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

27 Aug 202124 Nov 2023

First posted21 Feb 2021
Study start27 Aug 2021
Primary completion24 Nov 2023
Study completion24 Nov 2023

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (1)Papers the sponsor has linked to this study.
Other trials for COVID-19 PreventionStudies of the same condition, open and under way.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 2
Primary purpose: Prevention
Allocation: Not applicable
Intervention model: Single group
Masking: None (open label)
Enrolment: 51 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04765384
Sponsor's protocol ID: CR108962
Other IDs: VAC31518COV2004, 2020-005330-14
Acronym: HORIZON 1
Status last verified: May 2025
First submitted: 19 Feb 2021
Last updated: 25 May 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: The data sharing policy of the Janssen Pharmaceutical Companies of Johnson \& Johnson is available at www.janssen.com/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at yoda.yale.edu
Expanded access: Available

Publications

Aguilar G, Tapia-Calle G, Robinson C, Baron B, Lowson D, Maximos B, Rezelj VV, de Groot AM, Bet N, van Paassen V, Le Gars M, Struyf F, Ruiz-Guinazu J. Safety, immunogenicity and pregnancy outcomes in mothers and infants after vaccination with an adenovirus-vector COVID-19 vaccine during pregnancy. Hum Vaccin Immunother. 2025 Dec;21(1):2538340. doi: 10.1080/21645515.2025.2538340. Epub 2025 Aug 13.
PubMed 40808283

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 25 May 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: An Open-label, Phase 2 Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of Ad26.COV2.S in Healthy Pregnant Participants
ClinicalTrials.gov ID: NCT04765384
Acronym / sponsor ID: HORIZON 1 / CR108962
Conditions: COVID-19 Prevention
Phase: Phase 2
Study type: Interventional
Recruitment status: Completed
Enrolment: 51 participants (actual)
Lead sponsor: Janssen Vaccines & Prevention B.V.Industry (pharma, biotech, devices)
Study start: 27 Aug 2021 (actual)
Primary completion: 24 Nov 2023 (actual)
Study completion: 24 Nov 2023 (actual)
First posted: 21 Feb 2021 (actual)
Results: Posted 13 Nov 2024

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Detailed description

Study design

Primary purpose: Prevention
Allocation: Not applicable
Intervention model: Single group
Masking: None (open label)
Number of arms: 1

Arm	Type	Receives
Groups 1-4: Ad26.COV2.S (One Dose)	Experimental	Biological: Ad26.COV2.SParticipants who are previously vaccinated (Group 1-3) and participants who are vaccine naïve (Group 4) will receive single dose of Ad26.COV2.S vaccine at standard dose level on Day 1. Participants from group 4 who are no longer pregnant may receive single booster dose of Ad26.COV2.S vaccine at standard dose level.

Who may qualify

Ages: 18 to 45 years
Sex: Female only
Healthy volunteers: Accepted
Age groups: Adult

Key inclusion criteria (6 listed)

If on medication for a condition, the medication dose must have been stable for at least 4 weeks preceding vaccination
Participant must be healthy as confirmed by medical history, physical examination, vital signs, and obstetric history performed at Screening. Participant may have underlying illnesses, as long as the symptoms and signs are medically controlled
Participant will be at second or third trimester of pregnancy, that is, Week 16 to Week 38 of gestation (inclusive), at the time of vaccination, based on ultrasound at the time of screening (or not longer than 10 days prior to vaccination if performed elsewhere)
Participant agrees to not donate bone marrow, blood, and blood products from the first study vaccine administration until 3 months after receiving the last dose of study vaccine
Participant must be willing to provide verifiable identification, has means to be contacted and to contact the investigator during the study

Key exclusion criteria (8 listed)

Participants with medical or obstetric histories that put them at higher risk for maternal or fetal complications (example, chronic pregnancy-related disorders, birth defects or genetic conditions during previous pregnancy)
Participant with abnormal pregnancy screening test (example, ultrasound fetal abnormalities, maternal blood screen)
Participant has a history of malignancy within 2 years before screening (exceptions are squamous, basal cell carcinomas of the skin, carcinoma in situ of the cervix, or malignancy, considered cured with minimal risk of recurrence)
Participant has a known or suspected allergy or history of anaphylaxis or other serious adverse reactions to vaccines or their excipients (including specifically the excipients of the study vaccine)
Participant has a history of any serious, chronic, or progressive neurological disorders or seizures including Guillain-Barre syndrome, with the exception of febrile seizures during childhood

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
Ad26.COV2.SAlso: JNJ-78436735, Ad26COVS1Participants will receive intramuscular (IM) injection of Ad26.COV2.S.	Biological	Groups 1-4: Ad26.COV2.S (One Dose)

Primary outcome

Number of Adult Participants With Solicited Local Adverse Events (AEs) for 7 Days Post First Vaccination
Time frame: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8)
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
Time frame: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8)
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
Time frame: From first vaccination on Day 1 up to 28 days post first vaccination (up to Day 29)
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 Serious Adverse Events (SAEs) From First Vaccination Until End of the Study (EOS)
Time frame: From first vaccination on Day 1 until end of study (up to post-partum [PP] Day 366 [Day 15 up to Day 554])
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 Adverse Events of Special Interest (AESIs) From First Vaccination Until EOS
Time frame: From first vaccination on Day 1 until end of study (up to PP Day 366 [Day 15 up to Day 554])
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 Medically Attended Adverse Events (MAAEs) Until 6 Months Post First Vaccination
Time frame: From first vaccination on Day 1 until 6 months post first vaccination (up to Day 183)
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
Time frame: From first vaccination on Day 1 until end of study (up to PP Day 366 [Day 15 up to Day 554])
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-Enzyme-linked Immunosorbent Assay (S-ELISA) in Adult Participants 28 Days Post First Vaccination
Time frame: 28 days post first vaccination on Day 1 (at Day 29)
Serological response to vaccination as measured by S-ELISA in adult participants 28 days post first vaccination was reported.

20 secondary outcomes

Group 4: Number of Adult Participants With Solicited Local AEs for 7 Days Post Booster Vaccination
Time frame: 7 days post booster vaccination (Day 84 up to Day 371)
Group 4: Number of Adult Participants With Solicited Systemic AEs for 7 Days Post Booster Vaccination
Time frame: 7 days post booster vaccination (Day 84 up to Day 371)
Group 4: Number of Adult Participants With Unsolicited AEs for 28 Days Post Booster Vaccination
Time frame: 28 days post booster vaccination (Day 84 up to Day 392)
Group 4: Number of Adult Participants With SAEs Post Booster Vaccination Until EOS
Time frame: From booster vaccination (Day 84 up to Day 364) until EOS (up to PP Day 366 [Day 366 up to Day 554])
Group 4: Number of Adult Participants With AESIs Post Booster Vaccination Until EOS
Time frame: From booster vaccination (Day 84 up to Day 364) until EOS (up to PP Day 366 [Day 366 up to Day 554])
Group 4: Number of Adult Participants With MAAEs Until 6 Months Post Booster Vaccination
Time frame: 6 months post booster vaccination (Day 84 up to Day 546)
Group 4: Number of Adult Participants With AEs Leading to Study Discontinuation Post Booster Vaccination Until EOS
Time frame: From post booster vaccination (Day 84 up to Day 364) until EOS (up to PP Day 366 [Day 366 up to Day 554])
Number of Adult Participants With Pregnancy Outcomes
Time frame: From first vaccination on Day 1 until PP Day 1 (Day 7 up to Day 163)
Number of Adult Participants With Pregnancy Related AEs Throughout Pregnancy
Time frame: From first vaccination on Day 1 until PP Day 1 (Day 7 up to Day 163)
Serological Response to First Vaccination as Measured by S-ELISA in Adult Participants at All Blood Collection Timepoints Post First Vaccination
Time frame: Day 1, Day 29, PP Day 1 (Day 7 up to Day 163), PP Day 183 (Day 189 up to Day 345)
Serological Response to First Vaccination as Measured by Virus Neutralization Assay (VNA) Titers, 28 Days in Adult Participants Post First Vaccination
Time frame: 28 days post first vaccination on Day 1 (at Day 29)
Group 4: Serological Response to Booster Vaccination Measured by Binding (S-ELISA) Antibody Titers in Adult Participants at Blood Collection Time Points Post Booster Vaccination
Time frame: Booster Day 1 (Day 84 up to Day 364), Booster Day 29 (Day 112 up to Day 392)
Group 4: Serological Response to Booster Vaccination Measured by Neutralizing (VNA) Antibody Titers in Adult Participants at Blood Collection Time Points Post Booster Vaccination
Time frame: Booster Day 1 (Day 84 up to Day 364), Booster Day 29 (Day 112 up to Day 392)
Serological Response to Vaccination as Measured by S-ELISA at Birth (That is, in Cord Blood) and at 2 Months and 6 Months of Age in Neonates and Infants Born to Adult Participants
Time frame: At birth (postnatal [PN] Day 1 [Day 7 up to Day 163]), 2 months (up to PN Day 61 [Day 67 up to Day 223]) and 6 months (up to PN Day 183 [Day 189 up to Day 345])
Serological Response to Vaccination as Measured by VNA Titers at Birth (That is, in Cord Blood) in Neonates and Infants Born to Adult Participants
Time frame: At Birth (PN Day 1 [Day 7 up to Day 163])
Number of Neonates and Infants With SAEs (Including MIS-C) From Birth Up to 12 Months of Age in Neonates and Infants Born to Adult Participants
Time frame: From birth (PN Day 1 [Day 7 up to Day 163]) up to 12 months of age (up to PN Day 366 [Day 372 up to Day 528])
Number of Neonates and Infants With AESIs From Birth Until 12 Months of Age in Neonates and Infants Born to Adult Participants
Time frame: From birth (PN Day 1 [Day 7 up to Day 163]) until 12 months of age (up to PN Day 366 [Day 372 up to Day 528])
Number of Neonates and Infants With MAAEs From Birth Until 6 Months of Age in Neonates and Infants Born to Adult Participants
Time frame: From birth (PN Day 1 [Day 7 up to Day 163]) until 6 months of age (up to PN 183 [Day 189 up to Day 345])
Number of Neonates and Infants With AEs Leading to Study Discontinuation From Birth Until Study Discontinuation
Time frame: From birth (PN Day 1 [Day 7 up to Day 163]) until study discontinuation (until 12 months of age [up to PN Day 366 {Day 372 up to Day 528}])
Number of Neonates and Infants With Different Birth Outcomes From Birth Up to 12 Months of Age
Time frame: From birth (PN Day 1 [Day 7 up to Day 163]) up to 12 months of age (up to PN Day 366 [Day 372 up to Day 528])

Results and safety

Results posted to the registry on 13 Nov 2024, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
Group 1 (Adults): Ad26.COV2.S 5*10^10 vp	12	10
Groups 2 and 3 (Adults): Ad26.COV2.S 5*10^10 vp	10	8
Group 4 (Adults): Vaccine-naive: Ad26.COV2.S 5*10^10 vp	29	23
Group 1 (Neonates and Infants)	0	0
Groups 2 and 3 (Neonates and Infants)	0	0
Group 4 (Neonates and Infants)	0	0

Primary outcome: Number of Adult Participants With Solicited Local Adverse Events (AEs) for 7 Days Post First Vaccination

Time frame: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8). Count of participants. Unit: Participants

Measure	Group 1 (Adults): Ad26.COV2.S 5*10^10 vp n = 12	Groups 2 and 3 (Adults): Ad26.COV2.S 5*10^10 vp n = 10	Group 4 (Adults): Vaccine-naive: Ad26.COV2.S 5*10^10 vp n = 29
Value	10	5	20

Population analysed: Full Analysis Set - Adults (FAS-A) included all enrolled adult participants with at least one vaccine administration documented.

Primary outcome: Number of Adult Participants With Solicited Systemic AEs for 7 Days Post First Vaccination

Time frame: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8). Count of participants. Unit: Participants

Measure	Group 1 (Adults): Ad26.COV2.S 5*10^10 vp n = 12	Groups 2 and 3 (Adults): Ad26.COV2.S 5*10^10 vp n = 10	Group 4 (Adults): Vaccine-naive: Ad26.COV2.S 5*10^10 vp n = 29
Value	10	4	20

Population analysed: FAS-A included all enrolled adult participants with at least one vaccine administration documented.

Primary outcome: Number of Adult Participants With Unsolicited AEs for 28 Days Post First Vaccination

Time frame: From first vaccination on Day 1 up to 28 days post first vaccination (up to Day 29). Count of participants. Unit: Participants

Measure	Group 1 (Adults): Ad26.COV2.S 5*10^10 vp n = 12	Groups 2 and 3 (Adults): Ad26.COV2.S 5*10^10 vp n = 10	Group 4 (Adults): Vaccine-naive: Ad26.COV2.S 5*10^10 vp n = 29
Value	7	4	10

Population analysed: FAS-A included all enrolled adult participants with at least one vaccine administration documented.

Primary outcome: Number of Adult Participants With Serious Adverse Events (SAEs) From First Vaccination Until End of the Study (EOS)

Time frame: From first vaccination on Day 1 until end of study (up to post-partum [PP] Day 366 [Day 15 up to Day 554]). Count of participants. Unit: Participants

Measure	Group 1 (Adults): Ad26.COV2.S 5*10^10 vp n = 12	Groups 2 and 3 (Adults): Ad26.COV2.S 5*10^10 vp n = 10	Group 4 (Adults): Vaccine-naive: Ad26.COV2.S 5*10^10 vp n = 29
Value	4	2	3

Population analysed: FAS-A included all enrolled adult participants with at least one vaccine administration documented.

20 secondary outcomes are reported in the full results.

Adverse events

Time frame: Adult participants: From first vaccination on Day 1 until EOS (up to PP Day 366 [Day 15 up to Day 554]), Neonates & Infants: From birth (PN Day 1 [Day 7 up to Day 163]) up to 12 months of age (up to PN Day 366 [Day 372 up to Day 528]), Solicited AEs: From first vaccination on Day 1 until 7 days post first vaccination (up to Day 8), Group 4: Solicited AEs (booster vaccination): 7 days post booster vaccination (Day 84 up to Day 371). Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Group 1 (Adults): Ad26.COV2.S 5*10^10 vp	4 of 12 (33.3%)	12 of 12 (100%)	0 of 12
Groups 2 and 3 (Adults): Ad26.COV2.S 5*10^10 vp	2 of 10 (20%)	8 of 10 (80%)	0 of 10
Group 4 (Adults): Vaccine-naive: Ad26.COV2.S 5*10^10 vp	3 of 29 (10.3%)	27 of 29 (93.1%)	0 of 29
Group 1 (Neonates and Infants)	3 of 10 (30%)	7 of 10 (70%)	1 of 10
Groups 2 and 3 (Neonates and Infants)	4 of 8 (50%)	5 of 8 (62.5%)	0 of 8
Group 4 (Neonates and Infants)	4 of 29 (13.8%)	15 of 29 (51.7%)	0 of 29

Limitations and caveats (from the sponsor): Sample size for safety and immunogenicity analyses was low. In addition, further subdivision into subgroups by baseline serostatus and by baseline gestational age led to a further decrease in vaccination group sizes, making it difficult to draw any meaningful conclusions for the subgroup analyses.

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 25 May 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 40808283Aguilar G, Tapia-Calle G, Robinson C, Baron B, Lowson D, Maximos B, Rezelj VV, de Groot AM, Bet N, van Paassen V, Le Gars M, Struyf F, Ruiz-Guinazu J. Safety, immunogenicity and pregnancy outcomes in mothers and infants after vaccination with an adenovirus-vector COVID-19 vaccine during pregnancy. Hum Vaccin Immunother. 2025 Dec;21(1):2538340. doi: 10.1080/21645515.2025.2538340. Epub 2025 Aug 13.
Individual participant dataSharing planned: Yes. The data sharing policy of the Janssen Pharmaceutical Companies of Johnson \& Johnson is available at www.janssen.com/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at yoda.yale.edu

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Janssen Vaccines & Prevention B.V. Clinical Trial study director

Janssen Vaccines & Prevention B.V.

18 sites in 3 countries: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Ad26.COV2.S in people with COVID-19 Prevention, run by Janssen Vaccines & Prevention B.V. at 18 sites in 3 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 6 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 25 May 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 18 sites in Brazil, United States, South Africa. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 13 Nov 2024). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Number of Adult Participants With Solicited Local Adverse Events (AEs) for 7 Days Post First Vaccination (time frame: From first vaccination on Day 1 up to 7 days post first vaccination (up to Day 8)). The study lists 8 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04765384, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 25 May 2025.