The incidence of invasive pneumonia caused by Streptococcus pneumoniae in patients with AIDS dropped by over 50% in the first five years of HAART use, according to a US study published in the June 15th edition of the Journal of Infectious Diseases. However, the investigators found that, overall, individuals with AIDS were still 35 times more likely to develop invasive pneumonia than the HIV-negative, adult US population.
Bacterial pneumonia causes a significant amount of illness and death in HIV-positive individuals and can occur when an individual still has a relatively high CD4 cell count. Streptococcus pneumoniae is a major cause of bacterial pneumonia in patients who are both HIV-positive and HIV-negative.
Invasive pneumococcal disease occurs when S. pneumoniae penetrates normally sterile sites, such as the blood or cerebrospinal fluid. This occurs in between 15% and 30% of patients.
Investigators wished to establish trends in the incidence of invasive pneumoccal disease in adults aged 18 to 64 with AIDS in the first five years since the introduction of HAART. To do this the investigators used combined data from three US urban sites. Trends in pneumococcal disease in major subgroups of individuals with AIDS were also analysed. Annual data (July – June) from 1995 to 2000 were used.
A total of 539 cases of invasive pneumococcal disease in patients with AIDS were available for the investigators’ examination. Of these patients, 71% were male (53% black, 34% white, and 12% Hispanic) and 29% were women (77% black, 16% white, and 7% Hispanic).
In the first year of the study (1995-1996), the incidence of invasive pneumococcal disease was 1094 cases per 100,000 persons aged 18 – 64 with AIDS. This was 55 times higher than the incidence of the illness in HIV-negative adults. The annual incidence of invasive pneumonia in patients with AIDS dropped sharply in the next two years of analysis and then became relatively stable. The annual percentage declines in the incidence of invasive pneumococcal disease were -34%, -29%, -8%, and -1%.
Overall, the incidence of invasive pneumococcal disease fell by 57% during the five year period of the study.
The investigators then analysed their data by HIV risk subgroup. They found that the incidence of invasive pneumococcal disease fell in the five years of the study by 57% in men, 60% in women, 49% amongst whites, 67% amongst African Americans, and 46% amongst Hispanics.
“We observed a 57% decline in invasive pneumococcal disease incidence among persons with AIDS during the first five years after the introduction of HAART”, comment the investigators. “Most of this decline occurred between July 1995 and June 1998, when the use of protease inhibitors expanded rapidly in the United States.”
The investigators go on to add, “the magnitude and timing of declines were similar among men and women…whites…blacks, and Hispanics and across the three geographical areas studied.”
HAART was the primary explanation for the decline in the incidence of invasive pneumococcal disease, argue the investigators, “supported by the timing of its introduction into clinical practice, its demonstrated protective effect against bacterial infections, and the absence of alternative explanations.”
Nevertheless, the investigators note that in 2000 adult AIDS-patients were still 35 times more likely to become ill with invasive pneumonia then HIV-negative adults, leading the investigators to comment, “our data show that…persons with AIDS remain at extraordinarily high risk.”
Heffernan RT et al. Declining incidence of invasive Streptococcus pneumoniae infections among persons with AIDS in the era of highly active antiretroviral therapy, 1995 – 2000. J Infect Dis 191: 2038 – 2045, 2005.