With their immunocompromised status, HIV-infected children are at especially high risk for opportunistic infections, including infection by Streptococcus pneumoniae, hepatitis B, and measles. In PACTG P1024, HIV-infected children taking highly active antiretroviral therapy (HAART) received 2 doses of the pneumococcal conjugate vaccine (PCV), 1 dose of the pneumococcal polysaccharide vaccine (PPV), and booster shots of the hepatitis B vaccine (HBV) and measles, mumps, and rubella vaccine (MMR). Early responses to these vaccinations were favorable, but with declining antibody responses within the 18 months after vaccination. It is unknown if additional booster vaccinations in these children will result in a protective immunologic memory upon re-exposure to these pathogens. This study will determine whether HIV-infected children on HAART have evidence of specific immunologic memory 3 to 4 years after vaccination in PACTG P1024.