On Mar. 9, 2020, among African adolescent girls and young women who took HIV pre-exposure prophylaxis (PrEP) daily, levels of the PrEP drug tenofovir were more than 30% lower in those who were pregnant than in those who had recently given birth.

All 40 study participants took PrEP under direct observation, confirming their near-perfect adherence. PrEP drug levels were lower to a similar degree in the pregnant African adolescent girls and young women compared to American men and non-pregnant, non-lactating women who took PrEP daily under direct observation in an earlier study.

The study investigators suggest that nonetheless, daily PrEP may provide substantial protection for pregnant African adolescents and young women as part of a comprehensive HIV prevention program.

The substantially lower drug concentration found in dried blood spots from pregnant African adolescents and young women in the study does not necessarily indicate a lower PrEP efficacy for this group, according to the IMPAACT 2009 investigators. The response to any drug follows a curve that rises from zero as the dose increases until the curve reaches a plateau where a range of doses achieves a sufficient biological response to have the desired effect—in this case, preventing HIV infection. Based on available data, the study investigators believe the drug concentration in the target cells of pregnant adolescents and women who take PrEP daily will fall near this plateau. However, further research is required to establish whether this is the case.

The findings reported were from the first phase of the NIH-funded IMPAACT 2009 clinical trial. The study is designed to assess whether pregnant and postpartum adolescent girls and young women in southern and eastern Africa are willing and able to consistently take daily PrEP when given enhanced support, and whether PrEP is safe for them and their infants. Investigators hypothesize that pregnant and breastfeeding women may be uniquely motivated to start PrEP and take it consistently to protect themselves and their babies. A review of studies on the safety of PrEP for pregnant and breastfeeding women concluded that the benefits clearly outweigh potential risks.