inoculation (n.)

mid-15c. in horticulture, "act or practice of grafting buds;" 1714 in pathology, "insertion of a form of a virus in order to prevent a more serious attack of it," from Latin inoculationem (nominative inoculatio) "an engrafting, budding," noun of action from past-participle stem of inoculare (see inoculate).