Background: \- The Vaccine Research Center (VRC) is dedicated to understanding immune responses associated with prevention and treatment of infectious diseases. To study these immune responses, researchers need to collect specimens and images from individuals who have recently had a vaccination or recovered from an infection. These specimens and images are used to study different diseases and immune responses, and can be used to investigate ways to prevent or treat different medical conditions.

Objectives: \- To evaluate blood and other tissue samples for immune responses to vaccines and natural infections.

Eligibility: \- Healthy volunteers at least 18 years of age who agree to donate specimens for research purposes.

Design: * Participants will have clinical evaluations and will be asked to provide some of the following samples, depending on the research question being addressed. All procedures and sample donations are optional and voluntary: * Blood samples through regular blood draws (for whole blood) and apheresis (to collect specific parts of the blood such as plasma or white blood cells) * Urine, semen, saliva, or vaginal swab samples * Tissue samples or biopsy specimens * Undergo procedures such as bronchoscopy (lung and respiratory tract), gastrointestinal endoscopy (stomach and upper intestinal tract), or colonoscopy (lower intestinal tract) to obtain tissue samples * Undergo imaging studies such as positron emission tomography (PET) or computed tomography (CT) scans Duration of participation is variable depending on the research question but will usually last up to 1 year. \- Participants will be compensated for participation.