Care should be taken when promoting microbicide use among sex workers who are able to use condoms consistently: response to Smith et al. (2005)
Foss, Anna Ma; Watts, Charlotte Ha; Vickerman, Peter Ta; Heise, Lorib
aDepartment of Public Health and Policy, London School of Hygiene and Tropical Medicine, UK
bProgram for Appropriate Technology in Health (PATH), Washington, DC, USA.
Received 19 April, 2005
Accepted 10 May, 2005
In a recent paper in AIDS, Smith et al.  used mathematical modelling to explore the issue of condom migration, or ‘condom replacement’, on the potential impact of microbicide use by female sex workers. Similar to an earlier paper that we published , they developed a static model of the risk of HIV acquisition, and used this to obtain a threshold level of microbicide efficacy and use required to offset condom replacement. Although there are some differences in the mathematics used to formulate the risk of HIV infection and the scenarios considered, in most respects our two analyses yielded similar conclusions. In particular, both concluded that condom migration/replacement is not a substantial concern in populations that have low levels of condom use (as did Karmon et al.  in a similar analysis).
However, we are concerned that only the positive policy conclusions are presented by Smith et al.  with regard to condom replacement among sex workers: ‘For low/moderate efficacy microbicides, the risk of HIV acquisition in FSWs will be reduced – even if complete condom abandonment occurs – if prior condom use was low’.
This conclusion ignores the fact that, with proper counselling and support, sex workers can achieve a high rate of consistent condom use with their paying clients. A recent review of surveys of sex workers in Asia generally found that the median percentage reporting using a condom with their clients in the last sex act was over 75% [4,5]. There is also growing evidence across different settings that, following intervention, sex workers frequently achieve high levels of reported condom use with their clients [6–11], with as many as 96% of male military conscripts reporting using a condom at last commercial sex in northern Thailand, for example . Although there exist many sex worker populations who have low levels of condom use with their clients [5,12–15] (and many more that have not been studied), it is important to acknowledge when considering microbicide introduction scenarios that in some settings sex workers have attained high levels of condom use.
Our analysis suggests that among groups of sex workers with high levels of condom use, migration may be of concern. We found that if sex workers originally used condoms in over 53% of sex acts but abandoned condoms altogether after the introduction of a 50% efficacious microbicide, then the risk of HIV will increase even if microbicides are used in every sex act . If Smith et al.  had considered higher levels of condom use, they would have reached similar conclusions. For example, if Fig. 3 (b) had been extrapolated for higher levels of condom use, then a threshold for a 50% efficacious microbicide can also be seen . From this, it appears that if sex workers had originally used condoms in over 62% of sex acts but abandoned condoms altogether after microbicide introduction, then the risk of HIV will increase even if microbicides are used in every sex act.
Our analysis also showed that if a microbicide of 50% efficacy against HIV and sexually transmitted infections is used in 50% of sex acts not protected by condoms then high-consistency condom users (who use condoms in 90% of sex acts) could only reduce condom use to 86% without increasing the risk of HIV . However, this ‘high-consistency condom-user’ scenario was not discussed in the paper by Smith et al. .
The papers highlight the fact that further research is needed to explore the issue of microbicide introduction to sex workers. If women are able consistently to negotiate condom use with their clients, both models suggest that there may be risks associated with microbicide introduction if it weakens women's ability or resolve to negotiate condom use. At the same time, this result should not be used to withhold or limit the ability of sex workers to access microbicides . Clearly, there is an urgent need for microbicides, to provide additional protection to the many sex workers who are unable to negotiate consistent condom use with their clients [5,12–15], and to the many more who cannot use condoms in their non-commercial relationships (despite achieving high levels of use with clients) [4,5,9,11,17–19]. Instead, such studies raise important programmatic challenges about how best to promote microbicide use in a way that does not undermine consistent condom use, recognizing that there are small margins for error. For, although mathematics can provide a quantification of the risks and benefits, operational and social science research is needed to identify how best to respond.
The views and opinions expressed are those of the authors alone.
Sponsorship: This work is supported by the Global Campaign for Microbicides at PATH, with funding from the US Agency for International Development. P.V. and C.W. are part of the Microbicides Development Programme, which is funded by the UK Department for International Development (DFID). A.F., C.W. and P.V. are members of the DFID-funded HIV/AIDS and STI Knowledge Programme. The UK DFID supports policies, programmes and projects to promote international development.
1. Smith RJ, Bodine EN, Wilson DP, Blower SM. Evaluating the potential impact of vaginal microbicides to reduce the risk of acquiring HIV in female sex workers. AIDS 2005; 19:413–421.
2. Foss AM, Vickerman PT, Heise L, Watts CH. Shifts in condom use following microbicide introduction: should we be concerned? AIDS 2003; 17:1227–1237.
3. Karmon E, Potts M, Getz WM. Microbicides and HIV: help or hindrance? J Acquir Immune Defic Syndr 2003; 34:71–75.
5. Foss A, Watts C, Vickerman P, Kumaranayake L. HIV Tools Research Group, LSHTM. Are people using condoms? Current evidence from Sub-Saharan Africa and Asia and the implications for microbicides, November 2003
. Available at: http://www.ifh.org.uk/condom%20policy.htm
. Site accessed: 11 April 2005.
6. Ghys PD, Diallo MO, Ettiegne Traore V, Kale K, Tawil O, Carael M, et al
. Increase in condom use and decline in HIV and sexually transmitted diseases among female sex workers in Abidjan, Cote d'Ivoire, 1991–1998. AIDS 2002; 16:251–258.
7. Nelson KE, Eiumtrakul S, Celentano DD, Beyrer C, Noya Galai, Kawichai S, et al
. HIV infection in young men in Northern Thailand, 1991-1998: increasing role of injection drug use. J Acquir Immune Defic Syndr
8. Sanchez J, Campos PE, Courtois B, Gutierrez L, Carrillo C, Alarcon J, et al
. Prevention of sexually transmitted diseases (STDs) in female sex workers: prospective evaluation of condom promotion and strengthened STD services. Sex Transm Dis 2003; 30:273–279.
9. Ward H, Day S, Weber J. Risky business: health and safety in the sex industry over a 9 year period. Sex Transm Infect 1999; 75:340–343.
10. Wong ML, Chan R, Koh D. Long-term effects of condom promotion programmes for vaginal and oral sex on sexually transmitted infections among sex workers in Singapore. AIDS 2004; 18:1195–1199.
11. Foss AM, Watts CH, Vickerman P, Heise L. Condoms and prevention of HIV. BMJ 2004; 329:185–186.
12. Basuki E, Wolffers I, Deville W, Erlaini N, Luhpuri D, Hargono R, et al
. Reasons for not using condoms among female sex workers in Indonesia. AIDS Educ Prev 2002; 14:102–116.
13. Morison L, Weiss HA, Buve A, Carael M, Abega SC, Kaona F, et al
. Commercial sex and the spread of HIV in four cities in sub-Saharan Africa. AIDS 2001; 15(Suppl. 4):S61–S69.
14. Mgone CS, Passey ME, Anang J, Peter W, Lupiwa T, Russell DM, et al
. Human immunodeficiency virus and other sexually transmitted infections among female sex workers in two major cities in Papua New Guinea. Sex Transm Dis 2002; 29:265–270.
15. Ohshige K, Morio S, Mizushima S, Kitamura K, Tajima K, Suyama A, et al
. Behavioural and serological human immunodeficiency virus risk factors among female commercial sex workers in Cambodia. Int J Epidemiol 2000; 29:344–354.
17. Alary M, Mukenge-Tshibaka L, Bernier F, Geraldo N, Lowndes CM, Meda H, et al
. Decline in the prevalence of HIV and sexually transmitted diseases among female sex workers in Cotonou, Benin, 1993–1999. AIDS 2002; 16:463–470.
18. Wong ML, Lubek I, Dy BC, Pen S, Kros S, Chhit M. Social and behavioural factors associated with condom use among direct sex workers in Siem Reap, Cambodia. Sex Transm Infect 2003; 79:163–165.
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