One dose of the investigational vaccine or placebo will be given as a fourth booster dose. The vaccine will be administered intramuscularly at 3 dose levels or given as placebo (containing a 0.9 % NaCl solution), in combination with in vivo EP. The EP method used in the study is a class IIa EPS Gun from IGEA optimized for Electro Gene Transfer (EGT) vaccination and CE marked for the intended use in this clinical trial.~Primary objective:~• The primary objective of this study is to assess the safety and reactogenicity of the investigational vaccine OC-007 DNA delivered by in vivo EP, as a booster dose given at ≥ 3 months post-initial mRNA vaccination.~The secondary objectives:~• To investigate the humoral immune response to the investigational vaccine administered as one dose, by measuring changes in spike and of nucleocapsid antibody levels.~Exploratory objective:~To investigate in more detail the humoral response and analyze the cellular immune response to the investigational vaccine~To evaluate the number of SARS-CoV-2 infections documented by positive PCR test during the study period.
This is a randomized, placebo-controlled, double-blinded phase I study, designed to evaluate the safety including reactogenicity and immunogenicity of this investigational DNA vaccine delivered intramuscularly by in vivo EP in human adults. The vaccine doses will be given to healthy adults aged 18 to 60 years, who have been previously vaccinated against COVID-19 with 3 doses of either Comirnaty® or Spikevax®, or both in any combination ≥3 months ago.