This study will evaluate the efficacy of the Moderna COVID-19 vaccine against SARS-CoV-2 infection, as well as its effect on peak nasal viral load as a measure of infection and a proxy of infectiousness, in adults aged 18-29.~In the Main study, up to 12,000 participants will be randomized 1:1 to Immediate Vaccination Group 1 (at Months 0 and 1) or Standard of Care Group 2, with vaccination given at Months 4 and 5 if not received off-study previously. Up to an additional 6,000 participants will be enrolled into the Vaccine Declined Group 3 and will also be offered vaccine at Months 4 and 5.~Additional study visits for Group 1 will occur at Months 2 and 4; for Groups 2 and 3, at Months 0 and 2. Study visits may include medical history, vaccine injections, blood collection, nasal swab, SARS-CoV-2 screening, COVID-19 symptom check, and questionnaires.~In addition to the main study participants, the study will also evaluate infectiousness following close contacts with main study participants. Study procedures for close contacts include questionnaires and blood samples; for those who become SARS-CoV-2 infected, study procedures will also include nasal swabs.
The purpose of this study is to assess SARS CoV-2 infection, viral shedding, and subsequent potential transmission in individuals immunized with the Moderna COVID-19 vaccine.