Estrogen, Probiotics and Vaginal Health to Prevent HIV Infection in ACB Women

Inclusion Criteria: * African, Caribbean, Black * Pre-menopausal women in good general health, as determined by the investigator * Uterus and cervix present * 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/female doctor * Willing to abstain from vaginal intercourse for 48 hours prior to sampling, over the entire course of the study * Able to understand, comply and consent to protocol requirements and instructions * Able to attend scheduled study visits and complete required investigations Exclusion Criteria: * Currently lactating * Pregnant: suspected, current or in the last 12 months * Irregular menstrual cycle (less than 6 periods in a year) not related to contraceptive use, pregnancy or breastfeeding * Post-menopausal * Hormonal Contraceptive use or other hormonal treatment in the past 3 months * Current Intra-Uterine Device (IUD) use * Positive test result for Gonorrhea and/or Chlamydia * Clinically obvious genital ulceration/lesions * Symptomatic vaginal yeast infection or clinically significant vaginal discharge * HIV-positive * Any clinically significant abnormality on screening safety blood tests, that in the opinion of the investigator would preclude enrolment. * Diagnosed blood clotting disorder * Any genital tract procedure (e.g. biopsy) within the past 6 months * Use of oral probiotic supplement, oral antibiotics or oral steroids within the past 30 days * Current use of any vaginal products (except tampons) such as spermicides, microbicides, douching or drying products, antifungals, or steroids. * Known intolerance of Lactobacillus-containing probiotic supplements * Undiagnosed abnormal genital bleeding * Known, suspected, or history of breast cancer * Known or suspected estrogen-dependent malignant neoplasia (e.g. endometrial cancer) * Currently taking immunosuppressive drugs * Known or suspected hypersensitivity to any component of the Estring or RepHresh Pro-B products * Diagnosis of endometrial hyperplasia * Known liver dysfunction or disease; as long as liver function tests have failed to return to normal * Active or past history of arterial thromboembolic disease (e.g. stroke, myocardial infarction, coronary heart disease) * Partial or complete loss of vision due to ophthalmic vascular disease * Porphyria * Concomitant medication which in the opinion of the investigator may be associated with a significant drug interaction with the estrogen in Estring. * The conditions below are grounds for exclusion based on the opinion of the investigator: 1. Risk factors for estrogen dependent tumours, e.g. first degree heredity for breast cancer 2. Diabetes mellitus with or without vascular involvement 3. Migraine or (severe) headache 4. Epilepsy 5. A history of, or risk factors for, thromboembolic disorders 6. Systemic lupus erythematosus 7. Otosclerosis 8. Cholelithiasis 9. Leiomyoma (uterine fibroids) 10. Endometriosis 11. A history of endometrial hyperplasia 12. Hypertension 13. Asthma 14. Diagnosed anemia