A vaccine that prevents pregnancy in women (human chorionic gonadotropin / birth control vaccine).

During the early 1990s in India clinicians followed women who had at least 2 living children and were attending the family planning clinic at the All India Institute of Medical Sciences or Safdarjung Hospital in New Delhi or Postgraduate Institute of Medical Education and Research in Chandigarh to determine the efficacy of a birth control vaccine and if effective at what level of antibody titer it is effective. The vaccine was a heterospecies dimer of the beta subunit of human chorionic gonadotropin (hCG) and the alpha subunit of ovine luteinizing hormone (LH) conjugated to tetanus and diphtheria toxoids as carriers. Its aim was to induce antibodies of high avidity (Ka approximately equal to 10 billion M ) against hCG. 148 women received the 3 primary injections. 119 women (80%) produced hCG antibody titers greater than the hCG bioneutralization capacity (>50 ng/ml). The researchers determined efficacy based on women who completed 1224 cycles. Just one woman whose antibody titer was greater than 50 ng/ml conceived. In the absence of booster injections everyones antibody titers fell over time. 26 conceptions took place when titers fell below 35 ng/ml among women who did not effectively use other contraceptives. One woman who was protected from pregnancy for 12 cycles did not conceive until her antibody titers fell below 5 ng/ml. The cross-reactivity of the hCG antibodies to human LH were from 10% to 75% but the cross-reactivity did not impair ovulation or corpus luteum function and did not induce luteal insufficiency. These findings show that a contraceptive vaccine whose duration of effectiveness women can control themselves is likely.