Investigation of Immune Amnesia Following Measles Infection in Select African Regions

Inclusion Criteria: * Aged 1 to 15 years. * Ability of the participant's legal or culturally acceptable representative to provide informed consent. * Ability to give assent, as appropriate. * Stated willingness of parent/guardian and participant as appropriate, to comply with all study procedures. * Willingness to receive rabies vaccine. * Meet the criteria for assignment to Group 1 or Group 2, as follows: * Group 1, cases (acute MeV infection): * Clinical signs and symptoms suggestive of acute MeV infection (Koplik spots or skin rash) AND * Laboratory confirmed measles: * Upper respiratory specimen (swab) PCR for measles positive, OR * Serum IgM for measles positive. * Group 2, controls (no acute MeV infection): * No clinical signs and symptoms suggestive of acute MeV infection (Koplik spots or skin rash) AND * Upper respiratory specimen (swab) PCR negative for MeV AND * Serum measles IgM negative AND * Serum measles IgG positive and previously vaccinated for measles (2nd dose will be offered if appropriate). If serum measles IgG is negative, participant must be willing to be vaccinated regardless of prior measles vaccine history to meet this criterion. Exclusion Criteria: * HIV infection or any other immunosuppressive condition or medications. * Pregnant or lactating. * History of prior measles or immunologic evidence of prior measles in the absence of prior measles vaccination. * Severe anemia, defined as hemoglobin less than 8 g/dL. * Any acute or chronic condition which, in the opinion of the investigator, constitutes a contraindication to participation in this study.