Intravaginal Practices, Bacterial Vaginosis, and HIV Infection in Women: Individual Participant Data Meta-analysis

Abstract

Pooling of data from 14,874 women in an individual participant data meta-analysis by Nicola Low and colleagues reveals that some intravaginal practices increase the risk of HIV acquisition.

Abstract

Background

Identifying modifiable factors that increase women's vulnerability to HIV is a critical step in developing effective female-initiated prevention interventions. The primary objective of this study was to pool individual participant data from prospective longitudinal studies to investigate the association between intravaginal practices and acquisition of HIV infection among women in sub-Saharan Africa. Secondary objectives were to investigate associations between intravaginal practices and disrupted vaginal flora; and between disrupted vaginal flora and HIV acquisition.

Methods and Findings

We conducted a meta-analysis of individual participant data from 13 prospective cohort studies involving 14,874 women, of whom 791 acquired HIV infection during 21,218 woman years of follow-up. Data were pooled using random-effects meta-analysis. The level of between-study heterogeneity was low in all analyses ( I ² values 0.0%–16.1%). Intravaginal use of cloth or paper (pooled adjusted hazard ratio [aHR] 1.47, 95% confidence interval [CI] 1.18–1.83), insertion of products to dry or tighten the vagina (aHR 1.31, 95% CI 1.00–1.71), and intravaginal cleaning with soap (aHR 1.24, 95% CI 1.01–1.53) remained associated with HIV acquisition after controlling for age, marital status, and number of sex partners in the past 3 months. Intravaginal cleaning with soap was also associated with the development of intermediate vaginal flora and bacterial vaginosis in women with normal vaginal flora at baseline (pooled adjusted odds ratio [OR] 1.24, 95% CI 1.04–1.47). Use of cloth or paper was not associated with the development of disrupted vaginal flora. Intermediate vaginal flora and bacterial vaginosis were each associated with HIV acquisition in multivariable models when measured at baseline (aHR 1.54 and 1.69, p<0.001) or at the visit before the estimated date of HIV infection (aHR 1.41 and 1.53, p<0.001), respectively.

Conclusions

This study provides evidence to suggest that some intravaginal practices increase the risk of HIV acquisition but a direct causal pathway linking intravaginal cleaning with soap, disruption of vaginal flora, and HIV acquisition has not yet been demonstrated. More consistency in the definition and measurement of specific intravaginal practices is warranted so that the effects of specific intravaginal practices and products can be further elucidated.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Since the first reported case of acquired immunodeficiency syndrome (AIDS) in 1981, the number of people infected with the human immunodeficiency virus (HIV), which causes AIDS, has risen steadily. By the end of 2009, an estimated 33.3 million people were living with HIV/AIDS. At the beginning of the epidemic, more men than women were infected with HIV but now, globally, more than half of all adults living with HIV/AIDS are women, and HIV/AIDS is the leading cause of death among women of child-bearing age. In sub-Saharan Africa, where more than two-thirds of HIV-positive people live, the situation for women is particularly bad. About 12 million women live with HIV/AIDS in this region compared with about 8 million men; among 15–24 year-olds, women are eight times more likely than men to be HIV-positive. This pattern of infection has developed because in sub-Saharan Africa most people contract HIV through heterosexual sex.

Why Was This Study Done?

If modifiable factors that increase women's vulnerability to HIV infection could be identified, it might be possible to develop effective female-initiated prevention interventions. Some experts think that intravaginal practices such as cleaning the vagina with soap or a cloth increase the risk of HIV infection by damaging the vagina's lining or by increasing bacterial vaginosis (a condition in which harmful bacteria disrupt the healthy vaginal flora) but the evidence for such an association is inconclusive. In this meta-analysis, the researchers pool individual participant data from several prospective longitudinal cohort studies to assess the association between intravaginal practices and HIV acquisition among women in sub-Saharan Africa. Meta-analysis is a statistical method that combines data from several studies to get a clearer view of the factors associated with of a disease than is possible from individual studies. In a prospective longitudinal cohort study, groups of participants with different baseline characteristics (here, women who did or did not use intravaginal practices), who do not have the outcome of interest at the start of the study (here, HIV infection) are followed to see whether these characteristics affect disease development.

What Did the Researchers Do and Find?

The researchers pooled individual participant data from 13 prospective cohort studies in sub-Saharan Africa involving nearly 15,000 women, 791 of whom acquired HIV, and asked whether HIV infection within 2 years of study enrollment was associated with self-reported intravaginal practices. That is, were women who used specific intravaginal practices more likely to become infected with HIV than women who did not use these practices? After controlling for age, marital status, and the number of recent sex partners, women who used cloth or paper to clean their vagina were nearly one and half times more likely to have acquired HIV infection as women who did not use this practice (a pooled adjusted hazard ratio [aHR] of 1.47). The insertion of products to dry or tighten the vagina and intravaginal cleaning with soap also increased women's chances of acquiring HIV (aHRs of 1.31 and 1.24, respectively). Moreover, intravaginal cleaning with soap was associated with the development of bacterial vaginosis, and disrupted vaginal flora and bacterial vaginosis were both associated with an increased risk of HIV acquisition.

What Do These Findings Mean?

These findings suggest that some intravaginal practices increase the risk of HIV acquisition but they do not prove that there is a causal link between any intravaginal practice, disruption of vaginal flora, and HIV acquisition. It could be that the women who use intravaginal practices share other unknown characteristics that affect their vulnerability to HIV infection. The accuracy of these findings is also likely to be affected by the use of self-reported data and inconsistent definitions of intravaginal practices. Nevertheless, given the widespread use of intravaginal practices in some sub-Saharan countries (95% of female sex workers in Kenya use such practices, for example), these findings suggest that encouraging women to use less harmful intravaginal practices (for example, washing with water alone) should be included in female-initiated HIV prevention research strategies in sub-Saharan Africa and other regions where intravaginal practices are common.

Additional Information

Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000416

• The US National Institute of Allergy and Infectious Diseases provides information on HIV infection and AIDS and on bacterial vaginosis

• The US Centers for Disease Control and Prevention has information on all aspects of HIV/AIDS, including specific information about HIV/AIDS and women; it also has information on bacterial vaginosis (in English and Spanish)

• HIV InSite has information on all aspects of HIV/AIDS

• Information is available from Avert, an international AIDS nonprofit on all aspects of HIV/AIDS, including HIV/AIDS and women and HIV/AIDS in Africa (in English and Spanish)

• A full description of the researchers' study protocol is available

• Several Web sites provide information on microbicides Global Campaign for Microbicides, Microbicides Development Programme, Microbicides Trials Network, and International Partnership for Microbicides