Nairobi sex workers show sustained reduction in high risk sex

This article is more than 15 years old. Click here for more recent articles on this topic

Providing risk reduction services to female sex workers leads to sustained changes in behaviour, even after the level of that service is substantially reduced, according to follow-up data from a Kenyan trial published in the August 15th edition of the Journal of Acquired Immune Deficiency Syndromes.

For four years up to 2002, researchers from the Kibera HIV Study Group offered female sex workers peer- and clinic-based risk reduction counselling with regular screening and treatment for sexually transmitted infections (STIs) along with HIV counselling and testing.

Kibera in Nairobi is the largest slum in Africa with a population thought to be as high as one million. The programme was part of a trial of 341 female sex workers which compared the rates of STIs and HIV among a group of women given antibiotics once a month with another group given placebo.


person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.


Having symptoms.


statistical significance

Statistical tests are used to judge whether the results of a study could be due to chance and would not be confirmed if the study was repeated. If result is probably not due to chance, the results are ‘statistically significant’. 


A pill or liquid which looks and tastes exactly like a real drug, but contains no active substance.


Antibiotics, also known as antibacterials, are medications that destroy or slow down the growth of bacteria. They are used to treat diseases caused by bacteria.

Despite an association between bacterial STIs and HIV acquisition, taking azithromycin (Zithromax) once a month reduced the risk of acquiring an STI but not becoming infected with HIV (Kaul 2004).

But being part of the trial was associated with rapid changes in sexual behaviour including increased use of condoms and lower client numbers - and these changes were associated with reduced rates of both STIs and HIV.

These changes were well sustained throughout the trial although condom use started to fall among bar-based sex workers.

Now researchers have contacted 172 of the original study group. Although routine STI screening had stopped the women could still access medical care for symptomatic infections, but few had.

Quarterly peer-led sex worker community meetings continued up to 2006 and a local project had started to distribute free male and female condoms in bars, hotels and other sex work hotspots. The peer-led meetings provided a forum for women to discuss how to negotiate condom use with clients.

During the original trial the reported average number of casual clients per week dropped from 16.2 to 2.8 (p0.001) (Ngugi 2007).

The researchers had devised a semi-quantitative measure of condom use for the trial which ranked frequency of use from 0 (no condom use) to 5 (100% condom use).

During the original trial condom use with casual clients went up from 2.6 to 3.7. But rather than falling after the trial ended, condom use increased further to 4.3 (p

Unprotected casual client encounters were calculated to have dropped more than 15-fold during the original trial from 393 to 24 per year (p

Part of the explanation for the reduction in client numbers may have been to do with the natural aging of the cohort and changes in life circumstances, but the researchers also found that as a result of peer-led discussions, women were also charging more for sex and so having fewer clients.

HIV incidence during the trial was 3.7 per 100 person years and at follow up was numerically lower at 1.6 per 100 person years. But this only represented three new cases and the difference was not statistically significant.

The authors say their results show that if quite low level community services can be maintained – such as free condoms and regular peer-led meetings – changes in behaviour can be sustained.

They admit that the risk reduction strategy used here would fall short of the best practice recommended by the Joint United Nations Programme on HIV/AIDS.

But it is reassuring that poorer resourced programs such as this may still be associated with significant and sustained changes, they conclude.


Kaul R et al. Monthly antibiotic chemoprophylaxis and incidence of sexually transmitted infections and HIV-1 infection in Kenyan sex workers: a randomized controlled trial. JAMA 2004 291: 2555-2562.

Ngugi E et al. Sustained changes in sexual behaviour by female sex workers after completion of a randomized HIV prevention trial. J Acquir Immune Defic Syndrome 2007, 45(5): 588-594.