Intradermal Administration of a COVID-19 mRNA Vaccine in Elderly (HVaNa)

Inclusion Criteria: Male or female aged ≥75 years at the moment of immunization. Healthy, determined by medical history and clinical judgement of the investigator. Participants with a pre-existing illness that is stable, defined as disease not requiring significant change in therapy or hospitalisation during the 6 weeks before enrolment and not expected to require any intervention during the study, can be included. Willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, and other study procedures. Willing to postpone their regular COVID-19 vaccination upon invitation by the Municipal Health Service or general practitioner until at least four months after receiving the intervention. Completed a primary series of COVID-19 vaccination. Capable and willing to give personal signed informed consent. Adequate understanding of the procedures of the study and agrees to abide strictly thereby. Fully conversant in the Dutch language. Agrees his/her general practitioner is informed about participation in the study. Agrees to provide access to information regarding their vaccination background. Agrees that the study physician and his/her delegates have access to their medical file at Radboudumc. Exclusion Criteria: Medical or psychiatric condition that may increase the risk of study participation or, in the investigator's judgement, make the participant inappropriate for the study. No decision-making capacity. History of severe adverse reaction to a vaccine or to any component of the study intervention. Thrombose with thrombocytopenia syndrome after vaccination with a COVID-19 vaccine. Dermatological conditions that might interfere with the ID vaccination. Receipt of COVID-19 vaccination within 3 months before receiving the study intervention. Known or suspected immunodeficiency, as determined by medical history or medication use (inhalation corticosteroids are allowed). History of autoimmune disease or an active autoimmune disease requiring therapeutic intervention. Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate IM injection. Participation in other studies involving other study interventions within 28 days prior and during 28 days after receiving the study intervention. Receipt of any other non-study vaccine within 28 days prior and after receiving the study intervention.