Question

what finally stopped the black death in europe?
herd immunity
vaccinations
lockdowns

Explanation:

The Black Death (bubonic plague) ended in Europe mainly due to herd immunity. Vaccinations were not available during that time (vaccination concepts came much later). Lockdown - like measures as we know now were not systematically implemented in the same way. Herd immunity occurs when a large enough portion of a population is immune (either through recovery from infection or other means) to make the spread of the pathogen difficult. In the case of the Black Death, after a large number of people either died or recovered (and likely had some level of immunity), the spread of the plague slowed and eventually subsided.

Answer:

herd immunity