A VACCINE THAT PREVENTS PREGNANCY IN WOMEN

We report here results of clinical trials on a birth control vaccine, consisting of a heterospecies dimer of the beta subunit of human chori onic gonadotropin (hCG) associated noncovalently with the alpha subuni t of ovine luteinizing hormone and conjugated to tetanus and diphtheri a toxoids as carriers, that induces antibodies of high avidity (K-a ap proximate to 10(10) M(-1)) against hCG. Fertile women exposed to conce ption over 1224 cycles recorded only one pregnancy at antibody titers of >50 ng/ml (hCG bioneutralization capacity). The antibody response d eclines with time; fertility was regained when titers fell to <35 ng/m l. This study presents evidence of the feasibility of a vaccine for co ntrol of human fertility.