This trial will study a self-amplifying mRNA (samRNA) based vaccine (GRT-R910) in previously vaccinated adults (≥18 years). GRT-R910 uses a codon optimized, prefusion stabilized Spike (S) cassette with additional T cell epitopes (TCEs) covering multiple epitopes from non-spike proteins to safely drive strong, broad, and durable B and T cell immune responses to SARS-CoV-2.
The primary objective is to assess the safety and tolerability of 2 different doses (10 or 30 mcg) of GRT-R910 when administered as a boost in healthy adults previously vaccinated with the AstraZeneca, Janssen/Johnson and Johnson, Moderna, or Pfizer/BioNTech COVID-19 vaccines.