inclusion criteria: 1. age ≥ 60 years. 2. adult in good health or with a stable health status if pre-existing medical history. stable health status is defined as an existing disease that has not required a significant change in treatment or hospitalisation for worsening in the 3 months prior to inclusion, and for which no significant change in treatment or hospitalisation for worsening of the disease is envisaged in the near future. 3. for participants over 60 years of age who participated in coviboost, to have received a booster dose of mrna vaccine (pfizer-biontech) administered at least 6 months before the 2nd booster dose 4. not included in coviboost (new participants to be recruited) and having received 2 doses of mrna vaccine (pfizer-biontech) with an interval of 3 to 6 weeks and a 1st booster dose of mrna vaccine (pfizer-biontech) or moderna administered at least 6 months before the 2nd booster dose 5. understands and agrees to comply with the study procedures. 6. written informed consent signed by the participant and the investigator. 7. person affiliated to a social security scheme.

inclusion criteria: 1. age ≥ 60 years. 2. adult in good health or with a stable health status if pre-existing medical history. stable health status is defined as an existing disease that has not required a significant change in treatment or hospitalisation for worsening in the 3 months prior to inclusion, and for which no significant change in treatment or hospitalisation for worsening of the disease is envisaged in the near future. 3. for participants over 60 years of age who participated in coviboost, to have received a booster dose of mrna vaccine (pfizer-biontech) administered at least 6 months before the 2nd booster dose 4. not included in coviboost (new participants to be recruited) and having received 2 doses of mrna vaccine (pfizer-biontech) with an interval of 3 to 6 weeks and a 1st booster dose of mrna vaccine (pfizer-biontech) or moderna administered at least 6 months before the 2nd booster dose 5. understands and agrees to comply with the study procedures. 6. written informed consent signed by the participant and the investigator. 7. person affiliated to a social security scheme.

inclusion criteria: age ≥ 60 years. adult in good health or with a stable health status if pre-existing medical history. stable health status is defined as an existing disease that has not required a significant change in treatment or hospitalisation for worsening in the 3 months prior to inclusion, and for which no significant change in treatment or hospitalisation for worsening of the disease is envisaged in the near future. for participants over 60 years of age who participated in coviboost, to have received a booster dose of mrna vaccine (pfizer-biontech) administered at least 6 months before the 2nd booster dose not included in coviboost (new participants to be recruited) and having received 2 doses of mrna vaccine (pfizer-biontech) with an interval of 3 to 6 weeks and a 1st booster dose of mrna vaccine (pfizer-biontech) or moderna administered at least 6 months before the 2nd booster dose understands and agrees to comply with the study procedures. written informed consent signed by the participant and the investigator. person affiliated to a social security scheme.

inclusion criteria: age ≥ 60 years. adult in good health or with a stable health status if pre-existing medical history. stable health status is defined as an existing disease that has not required a significant change in treatment or hospitalisation for worsening in the 3 months prior to inclusion, and for which no significant change in treatment or hospitalisation for worsening of the disease is envisaged in the near future. for participants over 60 years of age who participated in coviboost, to have received a booster dose of mrna vaccine (pfizer-biontech) administered at least 6 months before the 2nd booster dose not included in coviboost (new participants to be recruited) and having received 2 doses of mrna vaccine (pfizer-biontech) with an interval of 3 to 6 weeks and a 1st booster dose of mrna vaccine (pfizer-biontech) or moderna administered at least 6 months before the 2nd booster dose understands and agrees to comply with the study procedures. written informed consent signed by the participant and the investigator. person affiliated to a social security scheme.