It is not known for certain when smallpox first appeared in Europe; however, the disease reached its highpoint in the seventeenth and eighteenth centuries, when it persisted as an endemic disease while periodically erupting as an epidemic. European literature testifies to the pervasiveness of smallpox, a disease that most would have had acquired in childhood. In the New World, the disease was experienced very differently. With no acquired immunities on the part of native populations, European explorers and colonists were responsible for devastating "virgin soil epidemics," one consequence of which was to pave the way for the importation of African slaves. The first practical public health measure to effectively combat smallpox, inoculation and later vaccination, achieved notable success but was not free of flaws and controversy.