About The Study

This pilot trial will compare the effects of low-dose estrogen, a probiotic, or both, to improve the health of the vaginal microbiota and decrease the risk of HIV infection in pre-menopausal women.

About The Disease

The risk of HIV acquisition in women is roughly double that of men, due in part to a risk of inflammation in the female genital tract. Susceptibility to sexual transmission of infections, such as HIV, can be affected by different levels and types of various naturally occurring bacteria (vaginal flora), known as the vaginal microbiota. The hormone estrogen is thought to encourage the development of type of bacteria (Lactobacilli) and decrease inflammation. Vaginal flora that may increase HIV susceptibility appears to be more common in Black and Hispanic women, compared to White and Asian women.

CTN 308 will test a whether a protective vaginal microbiota can be developed in African, Caribbean, and Black (ACB) women who have flora that may put them at a greater susceptibility to HIV infection.

Study Approach

This study aims to recruit 80 ACB women; participants will be randomized to receive a 30-day course of one of the following treatments:

  • A low-dose estrogen vaginal ring
  • A low-dose estrogen vaginal ring with a vaginal probiotic
  • A low-dose estrogen vaginal ring with an oral probiotic
  • A vaginal probiotic alone

Participants will undergo blood, vaginal, and cervical testing at baseline, during the study, and after completion of treatment. Participants will also be asked to take vaginal swabs at home, to be tested for microbial levels at a later date.

As a pilot study, CTN 308 will primarily focus on the safety and tolerability of these treatments in combination, however, changes in vaginal health, inflammation, and HIV susceptibility will also be investigated.

Eligibility Requirements


  • Women 18-49 years of age
  • Uterus and cervix present
  • Recruited through the Women’s Health in Women’s Hands (WHIWH) community Health Clinic
  • Able to understand, comply, and consent to protocol requirements and instructions
  • Able to attend scheduled study visits and complete required investigations
  • Negative pregnancy test
  • Currently practicing barrier or non-hormonal forms of contraception, and planning to continue, for the duration of the study (barrier contraceptive, abstinence)
  • Willing to undergo a pelvic exam by a female nurse
  • Willing to abstain from sexual activities for 48 hours prior to sampling

Not Allowed

Additional Information

If you would like more information on this clinical study, please refer to the principal investigators.

Principal Investigators

Here’s who is leading this study.

Can’t find what you’re looking for? Email ctninfo@hivnet.ubc.ca.

Participating Sites

Here’s where this study is being conducted.