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Pneumococcal Disease Rate Drops in HIV Group But Still Far Exceeds HIV-Negative Rate
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20th International AIDS Conference, July 20-25, 2014, Melbourne
Mark Mascolini
Invasive pneumococcal disease (IPD) incidence dropped sharply from 1996 to 2011 in a large Californian HIV group [1]. But incidence in people with HIV still exceeded that in matched HIV-negative people more than 6-fold at the end of follow-up.
Caused by Streptococcus pneumoniae, IPD yields a high burden of morbidity and mortality in people with HIV, observed Kaiser Permanente researchers who conducted this study. Climbing vaccination rates in HIV-positive people and the general population, plus better HIV control with antiretroviral therapy, probably combined to cut IPD rates in HIV-positive people, the Kaiser team surmised. But how those rates changed since the early days of antiretroviral therapy--and how they compare with HIV-negative people--are poorly understood.
To address those questions, Kaiser investigators compared IPD incidence and risk factors in HIV-positive adults who use the Kaiser Permanente healthcare network and a set of HIV-negative people matched by age, gender, first year of follow-up, and medical center. Cohort members were in care between 1996 and 2011. Follow-up continued until a person got diagnosed with IPD, left the Kaiser Permanente system, or died, or until the end of 2011.
The analysis involved 13,079 people with HIV and 137,643 without HIV. Age averaged 40.4 years in the HIV group and 39.7 years in the HIV-negative group. Respective proportions of men were 90.5% and 90.4%, of whites 60.8% and 50.9%, blacks 18.1% and 9.1%, and Hispanics 15.1% and 18.2%. HIV-positive people had significantly higher rates of ever smoking (47.4% versus 30.6%), diabetes (1.6% versus 1.1%), any cancer (2.6% versus 0.3%), and PPV23 vaccination (13.8% versus 3.0%).
IPD incidence over the entire study period measured 160 per 100,000 person-years in the HIV group and 8 per 100,000 in the HIV-negative group. Poisson regression analysis adjusted for age, gender, race/ethnicity, socioeconomic status, smoking, diabetes, hypertension, stroke, cardiovascular disease, cancer, and PPV23 use determined that HIV-positive people had a 13-fold higher IPD rate (rate ratio [RR] 13.0, 95% confidence interval [CI] 9.1 to 18.7).
IPV incidence in the HIV group plunged from 305 per 100,000 person-years in 1996-1999 to 88 per 100,000 in 2010-2011. Over the same period IPV incidence did not vary in the non-HIV group. Adjusted rate ratios comparing IPV incidence with versus without HIV dropped across the years but always remained substantially higher in the HIV group:
Adjusted rate ratios (95% CI) for IPV incidence with vs without HIV
-- 1996-1999: RR 18.5 (10.8 to 31.8)
-- 2000-2003: RR 13.4 (6.9 to 25.7)
-- 2004-2007: RR 15.6 (7.4 to 33.0)
-- 2008-2009: RR 5.4 (2.2 to 13.5)
-- 2010-2011: RR 6.6 (2.7 to 16.1)
In people with HIV three factors more than doubled IPD risk: black versus white race (RR 2.4, 95% CI 1.6 to 3.7), ever smoking (RR 2.2, 95% CI 1.4 to 3.4), and prior cancer diagnosis (RR 2.2, 95% CI 1.3 to 3.8). Compared with 1996-1999, IPD incidence was lower in 2000-2003 (RR 0.5, 95% CI 0.3 to 0.9), 2004-2007 (RR 0.4, 95% CI 0.2 to 0.7), 2008-2009 (RR 0.3, 95% CI 0.1 to 0.6), and 2010-2011 (RR 0.3, 95% CI 0.1 to 0.6). Age, gender, or PPV23 vaccination did not affect IPD risk in this analysis. PPV23 vaccination also had no impact in a separate analysis of IPD risk in the HIV-negative group.
The Kaiser team cautioned that results may not apply to women or to people without health insurance. They noted that follow-up ended in 2011, before use of the PCV13 vaccine in people with HIV. US guidelines on pneumococcal disease vaccination are online at the link in reference 2.
The researchers proposed that declining IPD incidence over the years in people with HIV could reflect increasing herd immunity because of pneumococcal vaccine use in children and/or successful treatment of HIV infection. But PPV23 use among HIV-positive adults "does not appear to have been particularly effective."
Reference
1. Silverberg M, Muthulingam D, Leyden W, et al. Invasive pneumococcal disease among HIV-positive and HIV-negative adults. AIDS 2014. 20th International AIDS Conference. July 20-25, 2014. Melbourne. Abstract TUPE041.
2. Centers for Disease Control and Prevention. http://www.cdc.gov/vaccines/vpd-vac/pneumo/vacc-in-short.htm#adult
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