 - Females of childbearing potential must have a negative pregnancy test on screening and the morning of each vaccination prior to receipt of the vaccine and must agree to use a highly effective method of birth control from screening through 3 months following last study vaccination. A highly effective method of birth control is defined as one with a failure rate of less than 1 per year. Acceptable birth control methods that meet this criterion include hormonal implants and injectables, combined oral contraceptives, intrauterine devices IUDs, female sterilization tubal ligation, sexual abstinence, or a vasectomized partner. 