A vaccine against HCG (Human Chorionic Gonadotrophin) for stopping pregnancy is under development.
I'm assuming this would be a permanent sterilization?
How would you "unvaccinate"?
HCG is a hormone for fat regulation too (Homeopathic HCG is used in a currently popular weight loss program).
"Human chorionic gonadotropin (hCG) is synthesized soon after fertilization and is essential for embryonic implantation. A an anti-hCG vaccine would be ideal for immuno-contraception."
Learn More -
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TD4-521MCG3-1&_user=10&_coverDate=03%2F09%2F2011&_rdoc=20&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235188%232011%23999709987%232921799%23FLA%23display%23Volume%29&_cdi=5188&_sort=d&_docanchor&_ct=20&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=574fa3f90e112db16b4a18b05e51943a&searchtype=aSource