8. Women of childbearing potential must have an acceptable method of contraception from 28 days prior to the 1st vaccination until at least 60 days after the 2nd vaccination. Acceptable methods of contraception include the following: -Prescription oral contraceptives, contraceptive injections, intrauterine device (IUD), implants, vaginal ring, double-barrier method, contraceptive patch, male partner sterilization, abstinence (defined as refraining from heterosexual intercourse during participation in the study [from 28 days before the first vaccination until at least 60 days after the last vaccination]). Women of non-childbearing potential, defined as postmenopausal (any age with amenorrhea for = / >12 months without other known or suspected cause for amenorrhea, or surgically sterile (hysterectomy, bilateral tubal ligation, obilateral oophorectomy, or successful Essure® placement (permanent, non-surgical, non-hormonal sterilization) with documented confirmation test at least 3 months after the procedure), are not required to use the birth control methods.