Washington D.C., USA, 22-27 July 2012www.aids2012.org

Equal behaviors, unequal risks:

The role of partner transmission potential in racial HIV disparities among men who have sex with men (MSM) in the United States

Eli Rosenberg

Department of EpidemiologyEmory University Rollins School of Public HealthAtlanta, GA

July 23, 2012

Colleen Kelley, Brandon O'Hara, Paula Frew, John Peterson, Travis Sanchez, Carlos del Rio, Patrick Sullivan

Emory University Center for AIDS

Research

Washington D.C., USA, 22-27 July 2012www.aids2012.org

• HIV prevalence among MSM is high and MSM continue to bear the burden of HIV incidence in the US

• Black MSM, particularly young black MSM, continue to be overrepresented among new infections

• Reasons for racial disparity remain unclear

• Unknown degree to which prevalence of HIV without viral suppression perpetuates incidence disparities

• Theoretically, greater likelihood of encountering a partner who might transmit HIV translates into increased incidence

HIV and MSM

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Measures of transmission risk for disparities research• How do we measure an individual’s risk of having unprotected

sex in a community?

• Suggests a measure that incorporates the spectrum of HIV infection, diagnosis, linkage to care, treatment, suppression

• Our toolkit of measures is limited for this tasko HIV prevalenceo Community viral loado Population viral load

• Need for a broad and relevant public health measure

Washington D.C., USA, 22-27 July 2012www.aids2012.org

• Proportion of individuals in whole population with a current VL sufficient to transmit HIV

A new measure: Transmission Potential Prevalence (TPP)

¿ h𝑤𝑖𝑡 𝑉𝐿≥400𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛

• Crosses prevalence with VL measures

• VL cut-point unknown for MSM. Used conservative estimate of 400 copies/ml.

Washington D.C., USA, 22-27 July 2012www.aids2012.org

What are the TPPs in the black and white MSM communities of Atlanta and how do

they relate to HIV risk?

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Study Design

Eligibility: > 18-39 years old, non-Hispanic black or white, had male sex in last 3 months, not in mutually monogamous relationship, reside in metro Atlanta

Recruitment: venue-time-space sampling

Baseline visit:o HIV testing: Rapid test, WB confirmatory, viral loadso Partnership-level behavioral questionnaire

709 men (399 B, 310 W) enrolled from 7/2010 - 6/2012

Prospective HIV/STI incidence cohort study of black and white MSM in Atlanta

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Demographics and outcomes

Black MSM

(n = 399)

White MSM

(n = 310)p

 Age, median 25 y 28 y < .0001Education > HS 74 % 89 % < .0001

Male partners, prev. 12 mo., median  5 7.5 < .0001

HIV Prevalence 42 % 14 % < .0001HIV Incidence, per 100 PY 6.4 1.0 0.006

More details:O’Hara et al TU PE-133

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Results: Viral load measures

More details:Kelley et al MO PE-264

  Mean log10(VL) p VL > 400

copies/ml p

A. Community VL        Black 2.5 0.74 48 % 0.93White 1.9 47 %

         B. Population VL        

Black 3.5 0.77 61 % 0.66White 4.1 57 %         C. Transmission Potential        

Black n/a 25 % < .0001White 8 %

Washington D.C., USA, 22-27 July 2012www.aids2012.org

• Translate TPP and partner selection patterns into probabilities that HIV-negative, black and white MSM might encounter a potentially transmitting partner

• Race-specific, deterministic modelso TPP represents partner poolo UAI racial mixing patterns

3 groups: black, white, other Racial exclusivity 70% Among non-exclusive men, mixing with 3 groups

o Monte Carlo simulation to estimate variability (x 100,000)

Behavioral model

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Results: Behavioral modelProbability of having ≥ 1 partner with HIV transmission potential

39%

18%

3 7

10 25

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• Despite similar CVL and PVL, sizeable racial differences in TPP and associated exposure risk

• Model results suggest limited ability of behavioral interventions alone to eliminate disparities

• Communities with high TPP should be focus of new resources to prevent transmission

• HIV surveillance systems can be adapted to include TPP to understand transmission risk in subgroups and make meaningful comparisons

Conclusions

Washington D.C., USA, 22-27 July 2012www.aids2012.org

• Current VL does not reflect durable virologic suppression

• Model does not account for other determinants of transmission

• UAI serosorting not included

• Does not explain what originally gave rise to disparities

Limitations

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Our data support targeting resources to dramatically reduce

TPP among black MSM by increasing testing, linkage, and

retention in HIV care in order to reduce disparities in HIV

incidence, supported by coordinated behavioral interventions to

increase effectiveness of treatment.

Relevance

Washington D.C., USA, 22-27 July 2012www.aids2012.org

Thank you !!

• R01-MH085600• R01-HD067111• KL2-RR025009

• P30 AI050409 (Emory CFAR)

Supported by NIH #:

InvestigatorsRecruitersEvent staffRetention specialistsData team

Our participants! Eli Rosenbergesrose2@emory.edu