Immunogenecity and Safety of VaccinemRNA-1273 in Elderly Volunteers (Over 65 y) Compared to Younger Ones (18-45y)

Inclusion Criteria: 1. At least 65 years old, at least 75 years old or 18 to 45 years old, depending on the group of inclusion. 2. Healthy adults, or stable medical condition for adults with pre-existing medical conditions. A stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during 3 months before enrolment, nor expected to require any significant change in therapy or hospitalization for worsening disease in foreseeable future. 3. Understands and agrees to comply with the study procedures (visits, phone calls) and provides written free informed consent. 4. Able to comply with study procedures based on Investigator judgement. 5. Affiliated to a social security system, (except state medical aid) Exclusion criteria: 1. Subject is ill or febrile (body temperature ≥ 38.0°C) within 72 prior hours or and/or symptoms suggestive of COVID-19 within the past 14 days at enrolment visit. (Ill or febrile participants may be re-scheduled within the inclusion period when no longer presenting symptoms) 2. History of documented COVID-19 (PCR+, antigenic test+ or chest TDM+ or serology SARS-CoV-2+) prior to first vaccine administration 3. Subjects with positive serology to SARS-CoV-2 at the enrolment visit 4. Subjects who already received another anti-SARS-CoV-2-vaccine 5. Subjects who received BCG given within the last year. 6. An immediate family member or household member of study staff. 7. Use of immunosuppressive drugs like e.g. corticosteroids at a dosage \> 10mg/day (excluding topical preparations and inhalers) within 3 months prior to enrolment or 6 months for chemotherapies 8. Received immunoglobulin or other blood product within 3 months prior to enrolment or planned receipt of immunoglobulin or a blood product through study completion. 9. Received any vaccination within 4 weeks prior to first injection or plan to receive a licensed vaccine 4 weeks after the last injection. 10. History of severe adverse reactions to vaccine administration, including anaphylaxis and related symptoms, such as rush, respiratory difficulty, angioedema and abdominal pain to vaccines, or history of allergic reaction likely to be exacerbated by any component of the anti-SARS-CoV-2-vaccine. 11. History of severe allergic event 12. Participation in another investigational clinical study (Jardé 1 or Jardé 2) within 4 weeks before the enrolment visits or planned before the study completion. 13. Known HIV, active HCV or HBV infection 14. Any pathological condition, such as cancer, which may be susceptible of reducing immunity response 15. Any bleeding disorder considered as contraindication to intramuscular injection or phlebotomy 16. The use of investigational Ig, investigational monoclonal antibodies or convalescent serum are not allowed during the study 17. Any condition which in the opinion of the investigator may interfere with the aim of the study 18. Pregnant or breastfeeding or positive pregnancy urine test at enrolment visit. 19. Woman in childbearing without efficacious contraception (in the opinion of the investigator) for 31 days after treatment (2nd vaccine injection) 20. People under legal protection measure (tutorship, curatorship or safeguard measures)