Immunogenicity of Novel H1N1 Vaccination Among HIV-Infected Compared to HIV-Uninfected Persons

Inclusion Criteria: * 18-50 years of age * Receiving the novel H1N1 vaccine (killed formulation) as part of routine clinical care * A military beneficiary who expects to remain in the local area for the next 6 months Exclusion Criteria: * Healthcare worker who is involved in direct patient care * Acute febrile illnesses within 30 days prior to H1N1 vaccination (e.g., pneumonia, influenza, ILI) * Diabetes type 1 or type 2 * Systemic steroid or immunosuppressive medication use within 4 weeks of vaccination * Active diagnoses of a cancer (non-melanoma skin cancer allowed). * History of organ transplant * Chronic active hepatitis B or C * Active illicit drug use or alcohol abuse * Blood transfusion within the last year * Allergy to eggs * Previous significant adverse reaction (e.g., anaphylaxis) to the seasonal influenza vaccination * History of serious reactions to any prior vaccination (e.g., Guillain Barre Syndrome (GBS)). * Received another vaccination in the last 4 weeks (receipt of seasonal influenza vaccination is allowed) * Among females of childbearing potential, pregnant or within 6 weeks of being postpartum * History of ILI which was confirmed as an H1N1 infection