A Study in Healthy Adults Having Received a Single Vaccine Administration to Support the Development of Immunological Assays

Inclusion Criteria: * Subjects who the investigator believes that they can and will comply with the requirements of the protocol (e.g. return for follow-up visits). * A male or female between, and including, 18 and 50 years of age at study start. * A subject having received a Yellow Fever (YF) vaccine on the day of study entry. * Written informed consent obtained from the subject. * Healthy subjects as established by medical history and clinical examination performed on the day of YF vaccination. * Female subjects of non-childbearing potential may be enrolled in the study. * Female subjects of childbearing potential may be enrolled in the study, if the subject: * has practiced adequate contraception for 30 days prior to study start, and * has agreed to continue adequate contraception during the entire study period. Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) within 30 days preceding study start, or planned use during the study period. * Concurrently participating in another clinical study, within 3 months preceding study start and at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational product (pharmaceutical product or device). * Clinically significant anaemia or any known condition as per medical history that would preclude the drawing of blood as described in the protocol. * Known previous infection with YF virus. * Previous vaccination against YF more than approximately 5 hours before the blood sampling at Visit 1. * Administration of immunoglobulins and/or any blood products within the 3 months preceding the study start or planned administration during the study period. * Chronic administration (defined as more than 14 days in total) of immunosuppressants or other immune-modifying drugs (including chloroquine) within six months prior to the study start. For corticosteroids, this will mean prednisone ≥ 10mg/day, or equivalent. Inhaled and topical steroids are allowed. * Receipt of live attenuated vaccines other than the YF vaccine during the period beginning 30 days preceding the blood sampling at Visit 1 or planned use during the study up to the blood sampling at Visit 2. * Receipt of inactivated influenza vaccines (seasonal or pandemic) during the period beginning 21 days preceding the blood sampling at Visit 1 or planned use during the study up to the blood sampling at Visit 2. * History of malignancy (unless there has been surgical excision followed by a sufficient observation period, of at least 5 years, to give a reasonable assurance of sustained cure and which, in the estimate of the investigator, is not likely to recur during the study period). * Any confirmed or suspected immunosuppressive or immunodeficient condition (including HIV, hepatitis B and hepatitis C), based on medical history and physical examination (no laboratory testing required). * Family history of congenital or hereditary immunodeficiency. * Major congenital defects or serious chronic illness. * Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination and medical history. * Acute disease and/or fever at the time of enrolment. * Known pregnant or lactating female, as per medical records. * Female planning to become pregnant or planning to discontinue contraceptive precautions. * History of chronic alcohol consumption and/or drug abuse. * Any condition that may preclude the compliance to the study protocol.