Laboratory Study of Licensed H1N1 Influenza Vaccines in HIV-1 Perinatally Infected Children and Youth

Inclusion Criteria: 1. Children and youth 6 months to \<25 years of age at study entry. 2. HIV infection, defined as positive test results obtained from 2 different samples. Tests may include two of the same type OR two different types of tests listed below, as long as there are positive test results obtained from 2 different samples: * HIV-1 antibody (ELISA + WB), obtained at age \>18 months * HIV-1 culture, any age * HIV-1 DNA PCR, any age * HIV-1 RNA PCR \>10,000 copies/mL, any age * Neutralizable HIV-1 p24 antigen obtained \>28 days of age 3. In the opinion of the investigator, the route of HIV-1 transmission is perinatally acquired. 4. Parent or legal guardian, youth of legal age, or subjects who are emancipated minors, who are willing and able to provide signed informed consent. 5. Planned receipt of one of the following FDA licensed Influenza A (H1N1) 2009 Monovalent Vaccines within 24 hours following study entry: * Group A: Influenza A (H1N1) 2009 Monovalent Vaccine (MedImmune FluMist®) * Group B: Influenza A (H1N1) 2009 Monovalent Vaccine (Novartis Fluvirin®) * Group C: Influenza A (H1N1) 2009 Monovalent Vaccine (Sanofi Pasteur Fluzone®) \*OR has received one of the above vaccines within 4 hours prior to study entry. Exclusion Criteria: 1. Has a history of probable or proven pandemic 2009 H1N1 Influenza A virus infection prior to study entry. 2. Has received seasonal FluMist vaccine within 2 weeks prior to study entry. 3. Has received any 2009 H1N1 vaccines prior to the day of entry. 4. Has received any immunoglobulin or blood products within 3 months prior to study entry. 5. Has any condition that would, in the opinion of the site investigator, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the study. 6. Use of anti-cancer chemotherapy or radiation therapy within the 36 months preceding study entry, or has immunosuppression as a result of an underlying illness or treatment (other than HIV-1 infection). 7. Has an active neoplastic disease. 8. Long term use of glucocorticoids, including oral or parenteral prednisone or equivalent (more than or equal to 2 mg/kg per day or more than or equal to 20 mg total dose) for more than 2 weeks in the past 6 months, or high-dose inhaled steroids (\>800 mcg/day of beclomethasone dipropionate or equivalent) within the preceding 6 months (nasal and topical steroids are allowed).