RecruitingPhase 1Biological interventionA Study Evaluating MDX2301 in Healthy Adults and Adults at Higher Risk for Severe COVID-19.This first-in-human study is designed to evaluate the safety, tolerability, pharmacokinetics, anti-drug antibodies, and neutralizing activity of MDX2301 administered by intravenous (IV), intramuscular (IM), or subcutaneous (SC) routes in healthy adults and adults at higher risk for severe COVID-19. Participants will receive single IV, IM, and SC doses of MDX2301 or placebo and a repeat IM or SC dose approximately 3 months apart of MDX2301 or placebo.