Hormonal contraception alters vaginal microbiota and cytokines in South African adolescents in a randomized trialOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This randomized crossover trial tested how three hormonal contraceptives affect the vaginal microbiota and genital inflammation in adolescents. The goal was to see which method might best support vaginal health and lower HIV risk. Participants were randomized to injectable norethisterone enanthate (Net-En), combined oral contraceptives (COC), or a combined contraceptive vaginal ring (CCVR) for 16 weeks, then crossed over to another method for 16 more weeks. Cervicovaginal microbiota was profiled by 16S rRNA gene sequencing, and 13 cytokines were measured at baseline, crossover, and exit.
Who was studied?
The substudy enrolled 130 HIV-negative, non-pregnant adolescent females in Cape Town, South Africa, with a median age of 17 years (interquartile range 16 to 18). At randomization, 45 received the vaginal ring, 45 received Net-En, and 40 received combined oral pills. A total of 108 reached the crossover visit and 94 completed the exit visit. This was part of the open-label UChoose contraceptive acceptability trial. Study arms were balanced at baseline for demographics, bacterial vaginosis, and sexually transmitted infection prevalence.
What were the most important findings?
Adolescents on combined oral pills had significantly lower vaginal alpha diversity than those on Net-En or the ring (adjusted p equals 0.009 and 0.021 at crossover). Pill users more often shifted to a Lactobacillus-dominated CST-III community. The diverse, bacterial-vaginosis-like CST-IV community dominated in the Net-En and ring arms. HIV risk-associated taxa were more abundant with the injectable and ring than with the pill. Six inflammatory cytokines, including IL-1beta, IL-6, and TNF-alpha, rose significantly in ring users. Higher inflammation tracked with higher diversity and CST-IV.
What are the greatest implications of this study?
The findings suggest that combined oral contraceptives may foster a healthier, less diverse vaginal ecosystem, which could benefit young women at high risk for bacterial vaginosis and HIV. The vaginal ring was linked to the most genital inflammation. Because the trial was randomized, it avoids much of the confounding that limits observational contraceptive studies. The study was open-label, used lower-resolution V4 sequencing, and had loss to follow-up. It measured relative not absolute abundance, and cannot prove that these microbiota shifts change actual HIV acquisition.