Vaccination for contraception
Jones, W.R.
Australian and New Zealand Journal of Obstetrics and Gynaecology 34(3): 320-329
1994
ISSN/ISBN: 0004-8666 PMID: 7848209 DOI: 10.1111/j.1479-828x.1994.tb01082.xDocument Number: 286309
Considerable progress in the development of antigamete vaccines has been made. Potential targets are sperm acrosomal antigens and the ZP3 glycoprotein of the zona pellucida. Researchers aim to effect an immune attack on events linked to sperm-ovum contact and fertilization. Consumer health advocates are concerned that health authorities in developing countries may abuse contraceptive vaccines and that those in developed countries will use them in vulnerable groups, e.g., aborigines in Australia. Some women's groups worry that loss of control and lack of body awareness are inherent in these vaccines. Sperm vaccine research is not as advanced as that of ovum vaccine research. Almost all sperm vaccine research has occurred in animals with varying degrees of success. Research in zona pellucida vaccine development must overcome the risk of immune damage to ovarian oocytes, subsequent development of autoimmune oophoritis, and disturbed ovarian function. Some research is examining the development of contraceptive vaccines against embryonic and placental antigens. The contraceptive vaccine that is the most developed is a vaccine against the pregnancy hormone human chorionic gonadotropin (hCG). This vaccine will probably be the first vaccine available in family planning programs worldwide. The WHO vaccine directed against the C-terminal peptide of beta-hCG incites a specific and safe immune response. The Phase I trial showed that the hCG vaccine exceeded the threshold of antibody production needed to achieve protection against pregnancy in all 5 subject groups with antibody titers in the higher dose groups reaching 5-7 times the level assumed to produce antifertility efficacy. Phase 2 clinical trials of this vaccine will begin in 1994 in Sweden. Further developments with the hCG vaccine are replacement of the current emulsion vehicle by a biodegradable microsphere-delivery system which will allow a more sustained antigen release and duration of effectiveness.