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

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 peripheral blood of adult participants to Ad26.COV2.S administered IM as a 1-dose schedule during the second and/or third trimester of pregnancy, 28 days after vaccination.

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).

Eligibility Criteria:
Inclusion Criteria:

* 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

Exclusion Criteria:

* 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)