About The Study

The purpose of this study was to determine whether it was more effective for people living with HIV with a low CD4 cell count to receive a pneumonia vaccine immediately or if it was better to wait for HAART treatment to improve immune functions and then to provide the pneumonia vaccine. Participants presenting with CD4 counts below 200 cells/mm3 were either vaccinated immediately, or waited until their CD4 counts exceeded 200 cells/mm3 before receiving a vaccination. The study also set out to compare the effectiveness of two different pneumonia vaccines, polysaccharide (Pneumovax or Pneumo23) and heptavalent vaccine (Prevnar) for people living with HIV.

Study Approach

This was a multicenter, randomized trial, conducted at 14 institutions across Canada between September 2004 and October 2007. Target enrolment for the trial was 80 people. Participants presenting with CD4 counts below 200 cells/mm3 were randomly assigned to one of four groups: Group 1 received the polysaccharide (Pneumovax or Pneumo 23) immediately, Group 2 was given the heptavalent vaccine immediately, Group 3 received a delayed treatment of polysaccharide after immune recovery, and Group 4 received the heptavalent vaccine after immune recovery. Participants were assessed every three months for a year to monitor antibody response. Those in the delayed immunization group whose CD4 count did not reach 200 cells/mm3 after six months were offered a vaccination.


Seventy-nine participants were included in the study. The average age of participants was 41 years old and 78% were male. All participants had a CD4 count between 50 and 200 cells/mm3 at the time of their enrolment.


Results of the study found in favor of delaying pneumonia-related vaccines until immune system recovery. The researchers observed no differences between the two individual vaccines and the findings were consistent among the various HIV serotypes (virus variation) in the study.


Despite a decline in incidence of pneumonia-related illnesses and improved immune status in people living with HIV in Canada (since the advent of HAART), the risks still remain high in certain populations, especially in the context of late stage HIV diagnosis. The findings provide valuable information for prevention of pneumonia-related diseases in individuals with late stage HIV diagnosis.

Principal Investigators

Here’s who is leading this study.

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