Inclusion Criteria:  Adult person, man or woman, staff of the Clermont-Ferrand University Hospital (medical or paramedical, medico-technical or administrative caregiver), having received the second dose of vaccine (or the single dose if the single-dose vaccination schedule) against COVID- 19 3 months +/- 15 days before the inclusion visit, as part of the national vaccination campaign, regardless of the type of vaccine administered. For the subgroup included before vaccination (study of the pre-vaccination cellular response): Adult person, man or woman, staff of Clermont-Ferrand University Hospital (medical or paramedical, medico-technical or administrative caregiver), receiving the 1st injection on the same day or in the 7 days before the inclusion visit, regardless of the type of vaccine administered Commitment to respect the schedule of visits provided for in the research protocol Able to give informed consent to participate in research Affiliation to a social security scheme  Exclusion Criteria:  Pregnancy or breastfeeding in progress at inclusion, or planned during follow-up Person under guardianship, guardianship or legal protection Whether the vaccine received was experimental or not authorized Refusal of participation