Program Director/Principal Investigator (Last, First, Middle): Creech, Clarence B Supplement Abstract A Phase 1/2 Study of Delayed Heterologous SARS-CoV-2 Vaccine Dosing (Boost) after Receipt of EUA Vaccines. This project supports specific aims 2, 3, and 4 from the Vanderbilt UM1 application and is consistent with the terms of award. More specifically, this activity is designed to gain knowledge of the safety, tolerability, and immunogenicity of a boost vaccine using a heterologous platform with the homologous or variant spike lineage administered after an EUA primary dosing Specific Aim 2: Conduct multi-site and single site research evaluating the safety, efficacy, and immunogenicity of novel interventions. We propose a single site at Children’s Hospital of Philadelphia that will evaluate the immune response to COVID vaccines in pregnancy Specific Aim 3: Evaluate immune responses resulting from natural infection or vaccine administration. Central to this work will be the evaluation of immune responses to a COVID vaccine candidate. Specific Aim 4: Train future leaders in vaccinology and clinical trials. Similar to other studies conducted for COVID thus far, junior faculty and fellows will be trained in vaccine-related clinical studies and pandemic responsiveness. This request is to support COVID-19 clinical research, including site preparation, study implementation, and enrollment of participants in the above COVID-19 clinical research study. Work will include but is not limited to: site preparation activities; protocol development/revision; clinical study activities; laboratory processing and storage of samples; quality oversight; and manuscript development, as appropriate. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page