Safety and Immunogenicity of a Monovalent mRNA Vaccine Encoding Influenza Hemagglutinin in Adult Participants 18 Years of Age and Older

Approximately 6 months

• Influenza Hemagglutinin mRNA vaccine (Biological): Pharmaceutical form:Solution for injection-Route of administration:IM injection
• Quadrivalent Recombinant Influenza Vaccine (Biological), also known as RIV4, Flublok Quadrivalent®: Pharmaceutical form:Solution for injection-Route of administration:IM injection

Primary outcomes

• Presence of any unsolicited systemic adverse events (AEs) reported in the 30 minutes after injection [Within 30 minutes after injection]: Number of participants with unsolicited systemic immediate adverse events (AEs)
• Presence of solicited injection site reactions (ie, pre listed in the participant's diary card [DC] and in the electronic case report form [eCRF]) occurring up to 7 days after injection [Up to 7 days after injection]: Number of participants with solicited injection site reactions
• Presence of solicited systemic reactions (ie, pre-listed in the participant's DC and in the eCRF) occurring up to 7 days after injection [Up to 7 days after injection]: Number of participants with solicited systemic reactions
• Presence of unsolicited AEs reported up to 28 days after injection [Up to 28 days after injection]: Number of participants with unsolicited AEs
• Presence of medically attended AEs (MAAEs) reported up to 28 days after injection [Up to 28 days after injection]: Number of participants with medically attended adverse events (MAAE)s
• Presence of serious adverse events (SAEs) and adverse events of special interest (AESIs) throughout the study [From baseline up to 6 months]: Number of participants with serious adverse events (SAEs)
• Presence of out-of-range biological test results (including shift from baseline values) up to 28 days after injection [Up to 28 days after injection]: Number of participants with out-of-range biological test results

Secondary outcomes

• Hemagglutination inhibition (HAI) antibody (Ab) titers to homologous H3 strain at D29, D91, and D181 [At Day 29, Day 91, and Day 181]: Antibody titers are expressed as Geometric Mean Titers (GMTs)
• Individual HAI Ab titer ratio D29/D01, D91/D01, D91/D29, D181/D01, and D181/D29 [From baseline up to 6 months]: Ratios of antibody titers measured by HAI in each group before and after vaccination
• HAI Ab titer ≥ 40 [1/dil] at D29, D91, and D181 [At Day 29, Day 91 and Day 181]
• 2-fold and 4-fold rise in HAI titers from D01 to D91 and D01 to D181 [From Day 01 through Day 91 and Day 01 through Day 181]
• Neutralizing Ab titers to homologous H3 strain at D29, D91, and D181 [At Day 29, Day 91, and Day 181]
• Individual neutralizing Ab titer ratio D29/D01, D91/D01, D91/D29, D181/D01, and D181/D29 [From baseline up to 6 months]
• 2-fold and 4-fold rise in neutralizing titers from D01 to D91 and D01 to D181 [From Day 01 through Day 29 and Day 01 through Day 181]
• HAI Ab titers to selected heterologous H3 strains at D01, D29, D91, and D181 [At Day 01, Day 29, D91 and D181]
• Neutralizing Ab titers to selected heterologous H3 strains at D01, D29, D91, and D181 [At Day 01, Day 29, Day 91, and Day 181]

Sex: All, ages: 18 Years to any, accepts healthy volunteers

Inclusion Criteria:

* Having given written informed consent prior to undertaking any study-related procedure. Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply:
* Any subject who, in the judgment of the Investigator, is likely to be noncompliant during the study, or unable to cooperate because of a language problem or poor mental development.

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.