Establishing Immunogenicity and Safety of Needle-free Intradermal Delivery of mRNA COVID-19 Vaccine

Objectives Primary objective * to describe immunogenicity and safety in healthy volunteers of the needle-free intradermal delivery of a single fractional dose of 20µg mRNA-1273 LNP vaccine (Spikevax, Moderna) more than 3 months after primary vaccination with Comirnaty (Pfizer) vaccine and/or after have contracted COVID-19. Secondary objectives * to describe the kinetics of the SARS-CoV-2 anti-Spike1 (S1) and Region Binding Domain (RBD) IgG binding antibodies elicited by needle-free intradermal or intramuscular delivery of mRNA-1273 vaccine in healthy volunteers after a single fractional dose of 20µg mRNA-1273 LNP vaccine * to describe the kinetics of the SARS-CoV-2 neutralising antibodies elicited by needle-free intradermal or intramuscular delivery of mRNA-1273 vaccine in healthy volunteers after a single fractional dose of 20µg mRNA-1273 LNP vaccine Exploratory objectives: * to describe the kinetics of memory B-cell and plasma cell responses elicited by needle-free intradermal or intramuscular delivery of mRNA-1273 vaccine of a single fractional dose of 20µg mRNA-1273 LNP vaccine (Spikevax, Moderna) * to describe the interferon-gamma release in whole blood in response to SARS-CoV 2 peptides after needle-free intradermal or intramuscular delivery of mRNA-1273 vaccine of a single fractional doses of 20µg mRNA-1273 LNP vaccine (Spikevax, Moderna) Study design: This is a Phase 2a, open-label, randomised-controlled, proof-of-concept vaccine study Study population: Healthy volunteers aged 18 - 40 years who have been vaccinated with Comirnaty (Pfizer) vaccine at least 3 months before Intervention group: Participants will receive 20 µg of mRNA-1273 vaccine through the needle-free intradermal route using a micro-needle delivery system. Control group: Participants will receive 20 µg of mRNA-1273 vaccine through the intramuscular route Main study parameters/endpoints: * Solicited local reactions and systemic events self-reported by diary on a daily basis over a 2-week period, telephone interview on D4, as well as by on site visits on D15 and D29 * Adverse events (AEs) until two weeks after administration * Serious AEs (SAEs) until six months after administration * Seroconversion for anti-spike IgG antibodies (D29) * Geometric mean concentrations (GMC) for anti-spike IgG antibodies (D1, D29)