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Climbing Rectal Gonorrhea Rate But Falling HIV Rate in British MSM
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HIVR4P Virtual, January 27-28 and February 3-4, 2021
Mark Mascolini
Among men who have sex with men (MSM) attending sexual health clinics in England, new diagnoses of rectal gonorrhea rose from 2010 through 2018, according to results of a large 9-region study [1]. Rectal gonorrhea usually predicts new HIV rates because both infections spread via condom-free anal sex. But in this population new HIV diagnoses dropped over the study period.
Researchers from the University of Washington and Public Health England noted the need for a marker of "placebo" HIV incidence in future HIV prevention trials among MSM-because such trials cannot ethically include a placebo arm. If an MSM trial population has a high rectal gonorrhea rate, the researchers asked, does that mean men enrolling in an HIV prevention trial are being exposed to HIV, even if actual new HIV rates are low because of effective biomedical prevention? If the answer is yes, future HIV prevention trials could use rectal gonorrhea rates to "provide supportive evidence" that a biomedical prevention strategy works.
With this thinking in mind, the researchers set out to learn "whether there is a reliable ecological association between HIV incidence and new rectal gonococcal infection, in the absence of PrEP" (preexposure prophylaxis).
HIV infection and rectal gonorrhea share a sexual exposure route-condom-free anal sex with an already-infected partner. Data from trials with follow-up between 2001 and 2014 confirmed a strong association between HIV and rectal gonorrhea in MSM. But the approach to HIV prevention evolved dramatically starting in 2015. Research confirmed that either antiretroviral PrEP or an antiretroviral test-and-treat strategy can prevent HIV infection. Treatment as prevention led to more HIV testing, and to the concept that an undetectable HIV load means untransmittable HIV.
To address these issues, the researchers examined sexually transmitted infection (STI) data from Public Health England, a mandatory surveillance system that gathers STI data. They focused on HIV-uninfected MSM more than 16 years old who had repeat sexual health clinic visits within 2 years that included a test for HIV or another STI. The analysis excluded men using PrEP. The goal was to calculate overall HIV incidence and overall rectal gonorrhea incidence in each calendar year from 2011 through 2018.
The study population included up to 75,000 MSM making up to 371,000 total visits yearly.
Three quarters of the men were white, and the largest age cohorts were 30 to 34, 35 to 44, and 25 to 29. For the 2011-2018 study period, new rectal gonorrhea diagnoses ranged from 800 to 4500 per year, whereas new HIV infections ranged from 100 to 450 for each year.
In an analysis adjusted for age, race, region, and calendar year, getting diagnosed with rectal gonorrhea tripled a man's individual risk of HIV infection (hazard ratio 3.19, 95% confidence interval 2.71 to 3.76). But there was a strong negative association between HIV incidence and rectal gonorrhea over the years. In other words, HIV incidence was high and rectal gonorrhea incidence low in the earlier years of the study period (2011 to 2015). Then HIV incidence fell while rectal gonorrhea incidence rose in later years (2016 and 2017). And HIV incidence was lowest while gonorrhea incidence was highest in the final study year (2018). This strong negative association between HIV incidence and rectal gonorrhea proved consistent across the 9 regions of England studied.
The investigators summarized their two key findings this way: Although getting diagnosed with rectal gonorrhea "is a strong individual predictor of increased risk of HIV infection" among MSM attending a sexual health clinic, high rectal gonorrhea incidence "does not necessarily imply" high population-level HIV risk in that same group.
Why do individual and population-level risks of HIV differ in this MSM group? The researchers suggested evolving treatment and prevention of HIV are not synergistic with prevention of rectal gonorrhea. Specifically, increasing rates of HIV suppression with antiretroviral therapy from 2011 through 2018 would help prevent HIV acquisition over those years but would not cut the risk of rectal gonorrhea. The research team cautioned investigators that "interpretation of rectal [gonorrhea] as a correlate of HIV risk is complex and context-dependent."
Reference
1. Donnell D, Zewdie K, Ratna N, et al. For MSM attending sexual health clinics in England, rates of new HIV infections decreased and rates of new rectal GC diagnosis increased between 2010-2018. HIVR4P (HIV Research for Prevention) Virtual, January 27-28 and February 3-4, 2021. Abstract OA16.02.
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