Trends in HIV incidence among youth in Rakai, Uganda, during a recent 12-year period varied substantially by sex and age, according to a prospective population-based cohort study.¹ Among women aged 15–19, the rate of new infections declined by more than four-fifths during the study period; however, no change was found among women aged 20–24 or among men in either age-group. In addition, school enrollment increased, particularly among 15–19-year-olds, and rates of sexual initiation and marriage generally decreased; medical circumcision increased among males. The majority of the decline in HIV incidence among teenage women, according to the researchers, can be explained by the reduction in sexual initiation, which in turn was related to higher school enrollment.

In the study, Santelli and colleagues analyzed data from 15–24-year-olds who took part in one or more of the nine rounds of the Rakai Community Cohort Study that were conducted between 1999 and 2011. This period—the third decade of the HIV epidemic in the district—saw implementation of multiple HIV prevention and treatment programs, and came soon after introduction of a new national policy of universal primary education that abolished tuition fees. During community surveys conducted roughly annually, participants completed questionnaires about their demographic, behavioral, reproductive and health characteristics, and provided specimens for HIV and STI testing. The investigators evaluated trends in HIV acquisition and in risk factors; used univariate and multivariate analyses to assess correlations between these trends; and performed decomposition analysis to determine the extent to which various risk factors may have contributed to changes in HIV incidence.

Analyses were based on 22,164 participants aged 15–24 residing in 43 communities. The researchers found that the rate of new HIV infections acquired between survey rounds was consistently higher among female youth (10–16 per 1,000 person-years) than among their male counterparts (6–10 per 1,000 person-years). Over the study period, women aged 15–19 had an 86% reduction in HIV incidence (from 17 to 2 new infections per 1,000 person-years); in contrast, women aged 20–24 and men of either age-group had no change in HIV incidence. Overall, the prevalence of HIV infection fell among females (from 9% in 1999 to 6% in 2011), whereas it remained unchanged among males (2–3%).

Trends in risk factors showed that the proportion of youth enrolled in school increased among all subgroups, but especially among teenage women (from 26% to 59%) and men (from 43% to 66%); similarly, the proportion who had ever had sex decreased among all youth, but the decline was greatest among 15–19-year-old women (from 76% to 50%) and men (from 63% to 41%). The proportion who had ever been married fell among teenage women (from 46% to 24%), teenage men (from 5% to 1%) and men aged 20–24 (from 52% to 37%). Roughly one in six young men had been circumcised early in the study, but more than one in three had been by the end. Among sexually experienced youth, the proportion reporting two or more partners in the past year fell among all subgroups, but especially among 15–19-year-old women (from 11% to 6%) and men (from 39% to 20%). There was minimal change in consistent condom use over the past year with primary and other partners, other than slight increases with primary partners among 15–19-year-old women and 20–24-year-old men; of note, only 7% of women aged 20–24 reported always using condoms with their primary partner at the end of the study period. The prevalence of alcohol use in the past month declined in all groups.

In multivariate analyses, sexually experienced women who were enrolled in school had a lower risk of acquiring HIV than did their nonenrolled counterparts (incidence rate ratio, 0.3); sexually experienced women reporting more than two partners in the past year had a sharply higher risk of HIV than their peers reporting none (6.0). Among sexually experienced males, HIV infection was positively associated with having had more than two partners in the past year (rather than none), having ever been married and having used alcohol in the past month (2.2–5.8).

Decomposition analysis found that 71% of the reduction in HIV incidence among women 15–19 could be attributed to the decline in sexual initiation in this group, while the other 29% could be attributed to decreased acquisition of HIV among those who were sexually experienced. Further analyses indicated that the entire decline in sexual initiation was likely because of increased school enrollment.

The authors acknowledge several limitations of their study. For example, behaviors were self-reported, and the findings may not apply to all of Uganda or to other Sub-Saharan African countries. In addition, the survey did not capture data on school performance and developmental transitions, such as puberty, that may have influenced school enrollment. Nonetheless, the authors comment that their study’s results reinforce earlier findings that, for teenage Ugandan women, schooling may have a protective effect against HIV infection. They suggest that increasing access to education may be a key prevention strategy in this setting; however, they add that "the absence of a reduction in HIV acquisition among young adult men and women suggests that multiple HIV prevention efforts with youth are needed to reach the goal of an AIDS-free generation."—S. London

REFERENCE

1. Santelli JS et al., Trends in HIV acquisition, risk factors and prevention policies among youth in Rakai, Uganda, 1999–2011, AIDS, 2015, 29(2):211–219.