The idea that vaccination against components of the reproductive system, such as gametes or hormones (Figure 1), could be used to interfere with sexual maturation or with fertility has been around for some time [1, 2]. As far back as the 1920’s and 1930’s studies were being carried out even in the human species, involving injection of women with fresh semen or bovine sperm phospholipid in attempts to elicit immunological contraception. Research during the latter half of the 20 th century has investigated the ability of vaccination to either arrest or impair sexual maturation, or to provide permanent or reversible contraception in sexually mature individuals. Several vaccines have now been tested for potential use in wild, feral and domesticated animal populations [3] and have also been developed for use in humans to provide an additional contraceptive choice for both men and women.

Much of the drive to develop such vaccines for use in humans has arisen due to the pressure of increasing world population, and the inadequacy of current contraception. Forty percent of couples of reproductive age do not practice any form of contraception. Even when contraception is used it is often not used as effectively as it could be. These facts result in fifty percent of the 1 million new pregnancies each day being unintended. Even in the USA, where access to contraception is comparatively straightforward, forty six percent of women have had at least one elective abortion by the end of their child-bearing years. Therefore, there is a clear need for the increased use of contraception and for a wider choice of contraceptive options.