Henry Kissinger's "population control memorandum"

a.k.a. the National Security Study Memorandum 200 (NSSM200). The study mentioned that oil and mineral-rich Nigeria could easily cope with a far larger population and would gain sufficient status to compete with the US influence over Africa, and had recommended that 13 of the largest developing countries, Nigeria included, be targeted with aggressive campaigns of fertility control in order to "contain" their rise to power.

Consider the above with respect to all the controversy around contaminated polio vaccinations. The timeline definitely implicates a conspiracy for the general skeptic, or at least an eerie set of coincidences, if you're a die hard rejectionist.