Answer:
vaccination
allergic reaction
t-cells
eradicated
autoimmune disease
Europeans had been exposed to the virus that causes smallpox for many generations, allowing them to acquire immunity to the virus. Native Americans were not exposed to smallpox or similar viruses before, so they had no immunity to the virus. In modern times, before traveling abroad, a person often receives vaccinations or other medications to avoid contracting the diseases specific to that region of the world.
Explanation:
