Modelling the global competing risks of a potential interaction between injectable hormonal contraception and HIV risk

BACKGROUND: Some but not all observational studieshave suggested an increase in risk of HIV acquisition for women using injectable hormonal contraception (IHC). METHODS: We used country-level data to explore the effects of reducing IHC use on the number of HIV infections the number of live births and the resulting net consequenceson AIDS deaths and maternal mortality for each country. RESULTS: High IHC use coincides with high HIV incidence primarily in southern and eastern Africa. If IHC does increase the risk of HIV acquisition this could generate 27 000-130 000 infections per year globally 87-88% of which occur in this region. Reducing IHC use could result in fewer HIV infections but also a substantial increase in live births and maternal mortality in countries with high IHC use high birth rates and high maternal mortality: mainly southern and eastern Africa South-East Asia and Central and South America. For most countries the net impactof reducing IHC use on maternal and AIDS-related deaths is dependent on the magnitude of the assumed IHC-HIV interaction. CONCLUSIONS: If IHC use increases HIV acquisition risk reducing IHC could reduce new HIV infections; however this must be balanced against other important consequences including unintended pregnancy which impacts maternal and infant mortality. Unless the true effect size approaches a relative risk of 2.19 it is unlikely that reductions in IHC could result in public health benefit with the possible exception of those countries in southern Africa with the largest HIV epidemics.