PIP: A vaccination developed to control fertility has shown promise in human trials. The vaccine is based on a synthetic oligopeptide that correlates to the sequence of amino acids (between 109-145) of the carboxy-terminal of human chorionic gonadotrophin. After the efficacy of the vaccine was observed in baboons and after testing for toxicology, the vaccine was administered to 30 women who had been surgically sterilized. Some of the women were given a water-soluble synthetic adjuvant without any human chorionic gonadotrophin. All of the subjects received a deep muscle injection on 2 separate occasions with a 6 week interim between injections. In addition, all of the women had pre-existing immunity to diphtheria toxoid; and the vaccine was conjugated to diphtheria toxoid to form a hapten-carrier complex. No serious adverse effects were experienced by any of the subjects. The vaccine shows promise as a method of birth control because the antigen is produced transiently in the productive process; there is an immune response that is specific to the target hormone. All of the women tested produced a high enough level of antibody to inactivate the human chorionic gonadotropin created by an early implanting embryo. The exact measurements of these amounts will be calculated when the vaccine undergoes phase 2 clinical trials. The immuno-safety of the trial was good, and it is believed that assessment criteria for future vaccines have been established by this trial.