A BIRTH-CONTROL VACCINE IS ON THE HORIZON FOR FAMILY-PLANNING

Vaccines for control of fertility are likely to have an important impa ct on family planning methods. They are designed to act by mobilizatio n of an internal physiological process and do not require external med ication on a continuous basis. A number of birth control vaccines are at different stages of development, the most advanced being a vaccine inducing antibodies against human chorionic gonadotrophin (hCG). This vaccine consists of a heterospecies dimer (HSD, betahCG associated wit h alpha-subunit of ovine luteinizing hormone, betahCG:alphaoLH) linked to tetanus toxoid (TT) or diphtheria toxoid (DT) as carriers. The vac cine has recently passed an important milestone; it has completed the first leg of phase 11 efficacy trials. Women of proven fertility leadi ng active sexual life were protected from becoming pregnant at antibod y titres greater-than-or-equal-to 50 ng of hCG bioneutralization capac ity per ml. This vaccine has previously been demonstrated to be revers ible in its effect. It is free from any notable side-effects on endocr ine, cardiovascular and other body functions. Ovulation was not distur bed and menstrual regularity was maintained. A logistic disadvantage o f the present vaccine is the requirement for multiple injections. This is expected to be overcome by encapsulation of the requisite doses of the vaccine in biodegradable microspheres, which could be given at a single contact point for sustained antibody titres lasting over a year . A live recombinant vaccine has also been made that elicits high anti -hCG titres in monkeys for nearly 2 years following primary immunizati on and a booster at 8-9 months.