Baseline Assessment of Skin Resident Memory T Cells in Healthy Unvaccinated Participants

Inclusion Criteria: * BMI \>/=18,5 kg/m2 and ≤35 kg/m2 * Agreement to share and discuss participant's medical history and medical records when relevant with the study team * Able and willing to provide written informed consent * Agreement to refrain from blood donation and other vaccinations during the study Exclusion Criteria: * Participants with a confirmed flavivirus infection in the past * Participants who received a flavivirus vaccination prior to enrolment (e.g. YFV, Japanese encephalitis virus, tick-borne encephalitis virus, Dengue) * Receipt of any vaccine (licensed or experimental) within 30 days prior to enrolment or during the study * Active participation in another interventional clinical study with active substance intake or large medical procedures affecting the study procedures during or 1 month prior to enrolment * Participant has a clinically significant acute illness (this does not include minor illnesses such as diarrhea or mild upper respiratory tract infection) or temperature ≥38.0ºC within 24 hours prior to the visit; inclusion at a later date is permitted at the discretion of the investigator * Any confirmed or suspected immunosuppressive or immunodeficient state (incl. cancer and human immunodeficiency virus/hepatitis B virus infection); asplenia; recurrent severe infections and use of immunosuppressant medication (including antineoplastic and immunomodulating agents or radiotherapy) within the last 6 months prior to enrolment, except topical or short-term oral steroids (\<2 weeks of daily receipt of 20 mg of prednisone or equivalent). Refer to annex 1 for a list of immunosuppressive medication * Severe and/or uncontrolled cardiovascular disease, respiratory disease, gastrointestinal disease, liver disease, renal disease, endocrine disorder, psychiatric and neurological illness (mild/moderate well controlled comorbidities are allowed) * History of bleeding disorder (e.g. factor deficiency, coagulopathy or platelet disorder), or prior history of significant bleeding or bruising following venipuncture * Any significant disease, disorder or planned surgery which may affect the ability of the volunteer to participate in the study or impact (skin) immunity homeostasis * Suspected or known alcohol or drug dependency * Known pregnancy * Tendency to keloid (scar) formation in response to skin damage * Skin diseases or tattoo at the biopsy site * In the opinion of the investigator, unlikely compliance to the requirements of the study * History of thymus dysfunction (including myasthenia gravis, thymoma) or thymectomy * Individuals who are working at the investigational site or within the research team of this study * Participants who received immunoglobulins and/or any blood or blood derived products within 3 months preceding the study * Participants who are currently on anticoagulant therapy * Participants who are continuously using systemic antivirals