7. Women of childbearing potential must have a negative serum β-human chorionic gonadotropin (β-hCG) pregnancy test at screening and a negative urine β-hCG pregnancy test within 24 hours preceding receipt of each dose and agree to practice, if not already practicing, highly effective birth control measures from 28 days before the prime vaccination until at least 90 days after the boost vaccination. For women already practicing highly effective birth control measurements for at least 28 days at screening start, recruitment can occur as soon as all screening procedures are completed. The following birth control measure will be considered highly effective: