Risk of invasive pneumococcal disease remains high for people living with HIV

People who inject drugs have especially high risk

Michael Carter
Published: 06 August 2014

People living with HIV continue to be at increased risk of invasive pneumococcal disease, Danish investigators report in the online edition of Clinical Infectious Diseases. Even in the era of modern antiretroviral therapy, risk of the infection was 19-fold higher among people living with HIV compared to matched controls in the general population.

People living with HIV who inject drugs had an especially high risk of invasive pneumococcal disease, and the authors sugges, “[people who inject drugs] might be an important target group for pneumococcal immunization, since they had the highest susceptibility to the disease over time in spite of the availability of treatment.”

Streptococcus pneumoniae is an important cause of serious bacterial disease in people living with HIV, and rates of invasive pneumococcal disease have been reported to be up to 100 times higher among people living with HIV compared to the general population.

Investigators in Denmark wanted to see if the availability of effective HIV therapy and the introduction in 2007 of a childhood pneumococcal immunisation programme using a conjugate vaccine had reduced rates of invasive pneumococcal disease in people living with HIV.

They therefore compared rates of the disease between people living with HIV and matched controls. The study period was 1995 to 2012, which was divided into three periods to reflect developments in HIV treatment and care: 1995-96, pre-combination antiretroviral therapy (cART); 1997-99, early cART; 2000-12, modern cART.

Each participant living with HIV was matched with 19 controls from the general Danish population.

Invasive pneumococcal disease was diagnosed by either blood culture or cerebrospinal fluid culture.

The study population comprised 5362 people living with HIV and 101,869 matched controls. Invasive pneumococcal disease was diagnosed in 137 people living with HIV and 136 controls. The people living with HIV were younger than the controls at the time of diagnosis with the disease (40 vs 47 years) and were less likely to be diagnosed with meningitis (4% vs 10%).

Comparison between people living with HIV with and without invasive pneumococcal disease showed that those with the infection were more likely to be female (32% vs 24%, p = 0.03), have a history of injecting drug use (26% vs 10%, p < 0.001), have a lower current CD4 count (303 vs 338 cells/mm3, p = 0.05) and a lower nadir CD4 count (116 vs 183 cells/mm3, p < 0.001).

The incidence of invasive pneumococcal disease was 205 cases per 100,000 person-years of follow-up for people living with HIV compared to 13 cases per 100,000 person years of follow-up for the controls.

Overall risk of invasive pneumococcal disease was approximately 24-fold higher among people living with HIV compared to the controls (IRR = 23.7; 95% CI, 22.9-24.4, p < 0.001).

Risk of the disease declined among people living with HIV as antiretroviral therapy improved, but even in the modern HIV treatment era the risk remained significantly higher for people living with HIV compared to the controls (IRR = 18.9; 95% CI, 14.3-25.00, p < 0.001). Moreover, the risk of the disease remained unchanged throughout the study period for people living with HIV who inject drugs.

Among people living with HIV, smoking (RR = 1.34; 95% CI, 1.26-1.42, p < 0.001) and injecting drug use (RR = 2.51; 95% CI, 2.26-2.67, p < 0.001) were associated with an increased risk of pneumococcal disease. Risk of the infection was also increased by the presence of detectable viral load (RR = 1.88; 95% CI, 1.79-1.98, p < 0.01) and lower CD4 cell count.

The 30-day mortality rate was lower for people living with HIV compared to the controls (7% vs 14%). Age was the only independent risk factor associated with death.

“The incidence of invasive pneumococcal disease in HIV-infected individuals remained significantly higher than the incidence observed in HIV-uninfected individuals, in spite of the widespread use of cART in Denmark,” conclude the authors. “[People who inject drugs] have a remarkably high risk of invasive pneumococcal disease that hasn’t declined over time, and remain an obvious group for targeted immunization…injecting drug use, smoking and the receipt of cART are suitable targets for preventative measures.”

Reference

Harboe ZB et al. Incidence and risk factors for invasive pneumococcal disease in HIV-infected and non-HIV-infected individuals before and after the introduction of combination antiretroviral therapy: persisting high risk among HIV-infected drug users. Clin Infect Dis, online edition, 2014.