The purpose of this study is to determine whether people who are HIV-positive respond better to a vaccine for pneumonia-related disease when they are immunized immediately, or when immunization is delayed until the immune system has improved to a certain level. The study will also compare the effectiveness of polysaccharide and heptavalent vaccines.

A multicentre, randomized controlled trial using a two factorial design. Eighty patients will be randomly assigned to receive either Pneumovax (or Pneumo23 according to standard use at site) or heptavalent pneumococcal conjugate vaccine (Prevnar) prior to reconstitution of the immune system or will have immunization delayed until their CD4 count is greater than 200 cells/mm3 after the introduction of antiretroviral therapy. Randomization will be stratified by study centre. Variable block sizes will be used to try to prevent study personnel from guessing the next allocation. Random allocation lists will be generated by computer.

Inclusion Criteria:

• HIV-positive
• Between 18 and 65 years of age
• Have a CD4 cell count below 200 cells/mm3
• Willing to begin/change antiretroviral therapy
• Willing and able to provide informed consent

Exclusion Criteria:

• Pregnant or breastfeeding
• Have had previous pneumococcal vaccination
• Have had occurrence of pneumococcal infection (brain, blood or lung infections) in past 5 years
• Have hypersensitivity to components of either vaccine
• Have acute feverish illness at the time of vaccination
• Have had splenectomy (removal of the spleen)
• Have received treatment with IVIG within the last 6 months