Invasive pneumococcal diseases (IPD) remain a significant cause of morbidity and mortality in people living with HIV (PLWH) despite widespread use of HAART and availability of pneumococcal vaccines. The aim of our study was to measure incidence and risk factors for IPD (defined as culture of Streptococcus pneumoniae from blood, CSF or both) in a cohort of 3160 HIV-infected patients who attended a single ambulatory HIV care center in Dublin, Ireland from 2006-2015.
Incidence of IPD was determined as events per 100 000 person-years of follow-up. Poisson regression was used to assess linear trend in incidence over time. A nested case-control study (four controls per case) was used to assess risk factors for IPD.
There were 47 episodes of IPD recorded in 42 HIV-infected individuals (median [IQR] age 38 [33-43], 69% male, 86% IDU, median CD4 T-cell count 213 cells/mm3) over 16 008 person-years of follow-up (overall incidence rate of IPD, 293/100 000 person-years). Three patients had 2 episodes and one patient had 3 episodes of IPD during the study period. The overall case fatality rate was 14% (95% confidence interval (CI), 4-24).The incidence of IPD per 100 000 person-years decreased significantly over time from 728 [95% CI, 455–1002], to 242 (95% CI, 120–365) to 82 (95% CI, 40-154) in calendar periods 2006-2008, 2009–2012, and 2013–2015, respectively (P <0.01 for linear trend).
On multivariate analysis lower CD4 count was associated with IPD (p=0.01) while being on HAART and history of previous pneumococcal vaccine were negatively associated with IPD (p<0.01 and p=0.023 respectively).
The decrease in incidence of IPD observed is likely multifactorial relating to improved vaccination coverage in our cohort in the setting of an integrated vaccination programme, changes to HIV care guidelines driving earlier initiation of HAART, herd immunity conferred following introduction of conjugate pneumococcal vaccine (PCV) to the infant immunisation programme in 2008 and the changing demographics of individuals presenting with HIV infection.
Despite decreases observed, HIV-infected individuals remain at higher risk of IPD compared to the general population. PCV may confer greater protection in HIV-infected individuals and should be seen as a priority to ensure best protection for our patients.