This concern isn’t about the usual tetanus vaccine.
The World Health Organization and UNICEF are promoting a 3 shot series of tetanus vaccines in order to prevent neonatal tetanus. The babies are at risk from non-sterile conditions when the umbilical cord is cut after birth.
The Catholic Bishops in Kenya say that a vaccine containing beta-HCG antigens is being used.
There was a report on research on just such a vaccine since the 1970’s. Here’s an abstract on the vaccine from 1993: http://www.ncbi.nlm.nih.gov/pubmed/7683889
While the effects of the contraceptive vaccine were said to be reversible, it is true that the mechanism might not only prevent ovulation, it could also prevent implantation or cause an early abortion. So, not true “contraception,” but an abortifacient.
UNICEF and WHO deny any use of a contraceptive vaccine and – especially – any secret experiment. They claim that the tests run by the Bishops gave false readings.
I’m not sure who is right in this case. It depends on whether actual vials of the questionable vaccines or blood samples were tested and the dependability of the lab.
While I wouldn’t put it past some bureaucrat deciding to cut the birth rate in Kenya, neither would I be surprised if this turns out to be anti-vaccine hysteria due to the focus on vaccination of fertile women.