Which statements correctly explain why smallpox has been eradicated, but not malaria or cholera?
1 Cholera vaccines provide only short-term immunity.
2 Plasmodium antigens change during the life cycle.
3 Smallpox antigens remain stable.
4 Vaccines only work against viruses.
1, 2 and 3
2 )
1, 2 and 4
3 )
1, 3 and 4
4 )
2, 3 and 4
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