Vaccination for birth control.

The global population is currently expanding at the unprecedented rate of nearly 1 billion per decade, with 94% of the increase occurring in the developing world. New methods of fertility regulation are urgently needed, and the development of birth control vaccines by active immunization against antigens specific for reproduction has made substantial progress during the last two decades. These vaccines are meant to have an outstanding impact on future control of worldwide population growth by providing safe, effective, long-lasting and reversible contraception. The most advanced of these vaccines are based on the placental pregnancy hormone human chorionic gonadotropin (hCG), and have already entered clinical trials. However, immunological cross-reactivity and lack of efficacy of anti-hCG antibodies seriously challenge this strategy. Conversely, efforts to understand the molecular events involved in the fusion of sperm and egg have led to the identification of new target structures for the development of fertility-regulating vaccines. Herein, we summarize the current state of birth control vaccines and discuss the risks and drawbacks of this approach to fertility regulation.