- Women of childbearing potential must have used an acceptable method of contraception for 30 days prior to the vaccination, must agree to use an acceptable method of contraception during the study, and must not become pregnant for at least 28 days after the vaccination. A woman is considered of childbearing potential unless post-menopausal or surgically sterilized. (Acceptable contraception methods are restricted to abstinence, barrier contraceptives, intrauterine contraceptive devices or licensed hormonal products.)