- Of childbearing potential but agrees to practice effective contraception or abstinence for 4 weeks prior to and 8 weeks after administration of the influenza challenge virus. Acceptable methods of contraception include 1 or more of the following: 1) male partner who is sterile prior to the female participant s entry into the study and is the sole sexual partner for the female participant; 2) implants of levonorgestrel; 3) injectable progestogen; 4) an intrauterine device with a documented failure rate of <1%; 5) oral contraceptives; and 6) double barrier methods including diaphragm or condom with a spermicide.