The aim of the COVID-19 vaccine clinical development program is to develop a safe and effective vaccine for the prevention of COVID-19.

Currently, there is only limited availability of authorized/licensed vaccines for the prevention of coronavirus disease-2019 (COVID-19). 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 severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus spike (S) protein, which will be assessed in this study.

Also, different vaccination intervals and multiple lower dose levels compared to the dose levels in the first in human (FIH) study (VAC31518COV1001 [NCT04436276]) will be assessed. For adults, the study consists of: screening phase (28 days), vaccination phase (1-3 months) depending on the vaccination interval, and follow-up (12 months) and for adolescents, the study will consist of a screening phase (28 days), a vaccination phase (2 months), a booster vaccination 12 months after the first vaccination, and a follow-up phase (12 months after the booster vaccination). The study duration is approximately 15 months (Groups 1-5 and Group 7 [for participants for whom vaccination 2 was delayed]), 14 months (Group 7 [for participants for whom vaccination 2 was not delayed]), 16 months (Group 9), 20 months (Group 6), 19 months (Group 8) and 27 months (Group 10) in adult groups and approximately 25 months for adolescents group (Groups A to F). The adverse events and other safety assessments including vital signs measurements (heart rate, supine systolic and diastolic blood pressure, respiratory rate, and body temperature) and physical examinations will be assessed during the study.