 6. Females of childbearing potential who refuse to use an acceptable method of birth control for a period of 56 days before and after each vaccination. Adequate contraception is defined as hormonal e.g., oral, injection, transdermal patch, implant, cervical ring, barrier e.g., condom with spermicide or diaphragm with spermicide, intrauterine device e.g., IUD, monogamous relationship with vasectomised partner who has been vasectomised for 6 months or more prior to the subjects study entry, or abstain from heterosexual intercourse e.g., through sexual orientation or religious or other beliefs about premarital intercourse; 