<qa>  What is a method of birth control defined as?4. Willing and able to provide written informed consent after having been informed of the requirements and the restrictions of the study. Female subjects of childbearing potential must agree to use a highly effective method of birth control defined as those which result in a low failure rate i.e. less than 1 per year when used consistently and correctly such as sexual abstinence, vasectomised partner, non hormonal IUDs, double barrier methods, for instance, e.g. condom and spermicide cream. 