Effectiveness of BCG vaccination against Mycobacterium tuberculosis infection in adults: a cross-sectional analysis of a UK-based cohort

Background The roll-out of anti-retroviral therapy (ART) has changed contexts of human immunodeficiency virus (HIV) risk. Here, we summarise direct estimates of HIV incidence among adolescent girls and young women (AGYW) since ART and before large investments in targeted prevention for AGYW in sub-Saharan Africa. Methods Database searches identified studies reporting HIV incident data from serological samples collected among 15-24 year-old females in 10 countries selected for PEPFAR investment in 2015. Estimates collected between 2005-2015, published or received from authors, were summarised by age and sex, and pooled by region. Findings Fifty-one analyses were identified from nine of the eligible countries (save Lesotho). Directly-observed incidence rates were lowest among AGYW in Kumi, Uganda (0.38%) and highest in KwaZulu-Natal, South Africa (7.8% among 15-19y; 8.6% in 20-24y); fishing communities in Uganda (12.4% and 4.7% among 15-19y and 20-24y females); and among sex workers aged 18-24y in South Africa (13.2%) and Zimbabwe (10.8%). In pooled rates from general population studies, the greatest sex differentials were in the youngest age groups, i.e., 15-19y females compared to males in both Southern African (relative risk=5.94; 95% CI:3.39-10.44) and Eastern African countries (3.22; 95% CI:1.51-6.87), and not significantly different among the oldest (25-29y) in either region. Incidence often peaked earlier (during teenage years) among high-risk compared to general populations. Since 2005, AGYW incidence declined in Rakai (Uganda), Manicaland (Zimbabwe), and among sex workers in Kenya, but not in the highest-risk communities in South Africa. Interpretation Few sources of direct estimates of HIV incidence exist in high-burden countries and trend analyses with age/sex disaggregated data are rare but indicate recent declines among AGYW. In some of the highest-risk settings, however, little evidence exists to suggest ART availability and other efforts slowed transmission by 2016. Despite wide geographic diversity in absolute levels of AGYW incidence, risk relative to males persisted in all settings, with the greatest sex differentials in the youngest age groups. To end new infections among the growing population of adolescents in sub-Saharan Africa, prevention programs must address gender inequalities driving excessive risk among adolescent girls.