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JAIDS Journal of Acquired Immune Deficiency Syndromes:
doi: 10.1097/QAI.0b013e31818d5f9e
Letters to the Editor

Low HIV Seroincidence Among Female Commercial Sex Workers: A Barrier for Measuring HIV Vaccine Efficacy

Djomand, Gaston MD, MPH*; Beyrer, Chris MD, MPH†; Buchbinder, Susan MD‡

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*HIV vaccine trials Network Seattle, WA †Johns Hopkins Bloomberg School of Public Health Baltimore, MD ‡Department of Public Health San Francisco, CA

To the Editor:

We thank Barroso et al for providing a summary of their pilot study to evaluate methods and barriers to recruitment of commercial sex workers (CSWs) in Rio de Janeiro, Brazil. As they note, HIV efficacy trials require enrollment of large and diverse cohorts of participants that reflect the demographics of high-risk individuals. This may ensure that summary measures of efficacy are most applicable to populations in greatest need of HIV vaccines.1 Because vaccine effects could differ between female and male populations, as has been suggested from herpes vaccine trials,2,3 and because interpretation of surrogate endpoints (eg, viral load set point) may be influenced by gender,4,5 HIV vaccines should be evaluated in both populations, when possible.

In their study, Barroso et al report that despite extensive outreach, only 7.8% of CSWs visited the vaccine trial site and less than 1% actually enrolled in the Phase IIB trial. Several of the social and cultural barriers that they enumerate (eg, lack of understanding of rationale for vaccine trials, transportation, clinic hours, and lack of reliable contact information) are barriers that can be addressed through ongoing work within high-risk communities and innovative logistical solutions (eg, extended clinic hours, providing cell phone time and/or voicemail boxes, and use of community outreach workers). Such strategies often require long-standing relationships with communities at risk, ongoing community education, and sufficient resources to staff outreach and flexible clinic hours. When these strategies are implemented, female CSW populations can be successfully recruited and retained, as noted in our vaccine feasibility study6 and in the subsequent Phase IIB vaccine trial.7

However, one of the most important challenges remaining is to recruit female populations with high HIV incidence in the United States. One reason for low HIV incidence rates in these trials is likely due to the fact that all participants receive extensive risk reduction counseling and linkage to local prevention services, with resultant substantial declines in HIV risk.6,8 Another reason may be low HIV prevalence in male partners. In Brazil, for example, where a simultaneous focus on ensuring access to prevention and treatment services has helped keep the epidemic stable, national adult HIV prevalence has remained stable at 0.5% since 2000.9 In fact, a limited number of studies on HIV seroincidence estimates among CSWs in South America have acknowledged rates as low as 0%.10-13

Efforts are currently underway to develop and test novel strategies to recruit high-incidence cohorts of women into trials through 2 National Institutes of Health-funded clinical trials networks: the HIV Vaccine Trials Network and the HIV Prevention Trials Network. These efforts build upon the efforts of investigators like our Brazilian colleagues, and investigators in the previously reported HIV Vaccine Trials Network 903 study, to ensure that future HIV vaccine trials are able to fully evaluate vaccine effects in women.

Gaston Djomand, MD, MPH*

Chris Beyrer, MD, MPH†

Susan Buchbinder, MD‡

*HIV Vaccine Trials Network

Seattle, WA

†Johns Hopkins Bloomberg School of Public Health

Baltimore, MD

‡Department of Public Health HIV Research Section

San Francisco, CA

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REFERENCES

1. Buchbinder SP, Metch B, Holte SE, et al. Determinants of enrollment in a preventive HIV vaccine trial: hypothetical versus actual willingness and barriers to participation. J Acquir Immune Defic Syndr. 2004;36:604-612.

2. Bernstein DI, Aoki FY, Tyring SK, et al, and GlaxoSmithKline Herpes Vaccine Study Group. Safety and immunogenicity of glycoprotein D-adjuvant genital herpes vaccine. Clin Infect Dis. 2005;40:1271-1281.

3. Stanberry LR, Spruance SL, Cunningham AL, et al, and GlaxoSmithKline Herpes Vaccine Efficacy Study Group. Glycoprotein-D-adjuvant vaccine to prevent genital herpes. N Engl J Med. 2002;347:1652-1661.

4. Touloumi G, Pantazis N, Babiker AG, et al, on behalf of the CASCADE Collaboration. Differences in HIV RNA levels before the initiation of antiretroviral therapy among 1864 individuals with known HIV-1 seroconversion dates AIDS. 2004;18:1697-1705.

5. Donnelly CA, Bartley LM, Ghani AC, et al. Gender difference in HIV-1 RNA viral loads. HIV Med. 2005;6:170-178.

6. Djomand G, Metch B, Zorrilla CD, et al, and the 903 Protocol Team. The HVTN protocol 903 vaccine preparedness study: lessons learned in preparation for HIV vaccine efficacy trials. J Acquir Immune Defic Syndr. 2008;48:82-89.

7. Robertson M, Mehrotra D, Fitzgerald D, et al. Efficacy results from the Step Study(Merck V520Protocol 023/HVTN 502): a phase II test of concept trial of the MRKAd5HIV-1 Gag/Pol/Nef trivalent Vaccine[88LB]. Presented at: The 15th Conference on Retrovirus and Opportunistic Infections; February 3-6, 2008; Boston, MA.

8. Bartholow BN, Buchbinder S, Celum C, et al, and the VISION/VAX004 Study Team. HIV sexual risk behavior over 36 months of follow-up in the world's first HIV vaccine efficacy trial. J Acquir Immune Defic Syndr. 2005;39:90-101.

9. UNAIDS, WHO. AIDS Epidemic Update: March 2008. Geneva, Switzerland: UNAIDS; 2007.

10. Vignoles M, Avila MM, Osimani ML, et al. HIV seroincidence estimates among at-risk populations in Buenos Aires and Montevideo: use of the serologic testing algorithm for recent HIV seroconversion. J Acquir Immune Defic Syndr. 2006;42:494-500.

11. Gupta SB, Murphy G, Koenig E, et al. Comparison of methods to detect recent HIV type 1 infection in cross-sectionally collected specimens from a cohort of female sex workers in the Dominican Republic. AIDS Res Hum Retroviruses. 2007;23:1475-1480.

12. Bautista CT, Sanchez JL, Montano SM, et al. Seroprevalence of and risk factors for HIV-1 infection among female commercial sex workers in South America. Sex Transm Infect. 2006;82:311-316.

13. Soto RJ, Ghee AE, Nunez CA, et al, and the Estudio Multicentrico Study Team. Sentinel surveillance of sexually transmitted infections/HIV and risk behaviors in vulnerable populations in 5 Central American countries. J Acquir Immune Defic Syndr. 2007;46:101-111.

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