A Synthetic MVA-based SARS-CoV-2 Vaccine, GEO-CM04S1, for the Prevention of COVID-19 Infection

PRIMARY OBJECTIVE: I. Safety and tolerability of the synthetic MVA-based SARS-CoV-2 vaccine GEO-CM04S1 vaccine at three different dose levels (DL): 1.0x10\^7 plaque-forming unit (PFU)/dose, 1.0x10\^8 PFU/dose, and 2.5x10\^8 PFU/dose. (Phase I) II. Evaluate the safety profile of a single-dose vaccine boost at day 7 post-injection of GEO-CM04S1. (Phase II) III. Determine whether the GEO-CM04S1 dose levels tested (1.0x10\^7 or 1.0x10\^8) generate promising immune responses (\>5-fold increase of Spike IgG over baseline) after single-dose booster injection, and select a promising dose to use for further study. (Phase II) SECONDARY OBJECTIVES: I. Longitudinal evaluation of humoral immunity. (Phase I) II. Quality and properties of cellular and humoral immunity elicited as a result of the vaccination. (Phase I) III. Explore the role of two injections versus one injection, and evaluate a placebo group. (Phase I) III. Evaluate T cell-based antigen-specific immune responses at day 28 post-injection of single-dose GEO-CM04S1 vaccine boost. (Phase II) IV. Evaluate SARS-CoV-2 S and N-specific Th1 vs Th2 polarization. (Phase II) V. Assess levels of SARS-CoV-2 neutralizing antibodies and their activity against variants of concern (VOC) or variants of high consequence (VHC). (Phase II) VI. Estimate the durability of antibody-based immune responses in a 12-month time period. (Phase II) VII. Estimate the durability of T-cell-based immune responses in a 12-month time period. (Phase II) VIII. Estimate the incidence of COVID-19 Moderate and Severe disease during follow-up (12 months). (Phase II) IX. Evaluate the potential relationship between duration of immunity and COVID infection (incidence) over the 12-month study period. (Phase II) X. Summarize outcomes, primary and secondary endpoints, based on pre-study mRNA vaccine received. (Phase II) EXPLORATORY OBJECTIVES: I. Surveillance for incidental coronavirus disease 2019 (COVID-19) infection during follow-up (1 year). (Phase I) II. Quality and properties of cellular and humoral immunity elicited as a result of the vaccination. (Phase I) III. Evaluate activated/cycling, cytotoxic/helper, and memory phenotype markers. (Phase II) IV. Estimate SARS-CoV-2-specfic serum IgA and IgG over time. (Phase II) OUTLINE: This is a dose-escalation study. PHASE I: Participants are randomized to 1 of 3 arms. ARM I: Participants receive GEO-CM04S1 intramuscularly (IM) in the non-dominant upper arm on day 0 and day 28 in the absence of unacceptable toxicity. ARM II: Participants receive GEO-CM04S1 IM in the non-dominant upper arm on day 0 and placebo IM in the non-dominant upper arm on day 28 in the absence of unacceptable toxicity. ARM III: Participants receive placebo IM in the non-dominant upper arm on day 0 and day 28 in the absence of unacceptable toxicity. PHASE II: Patients are randomized to 1 of 2 arms. ARM I: Participants receive low dose GEO-CM04S1 booster IM in non-dominant upper arm on day 1 in the absence of unacceptable toxicity. ARM II: Participants receive high dose GEO-CM04S1 booster IM in non-dominant upper arm on day 1 in the absence of unacceptable toxicity. During Phase 1, participants are followed up at 7, 14, 28, 35, 42, 56, 90, 120, 180, 270, and 365 days. During Phase 2, participants are followed up at 7, 14, 28, 80, and 365 days.