[reformedliberal]

You don’t consider yourself “cured” of the possibility to contract smallpox? Polio?

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Do the vaccines for these diseases turn the recipients’ own cells into pathogen-producers for an unknown amount of time?

Do either have an animal reservoir?

[steve86]

My comment did not cover possible externalities.

[blackdog]

The smallpox vaccine was made by giving the recipient a case of cowpox, which was so close a cousin to smallpox that your human body assigned them both a full time killer immunity response. Thus attacking smallpox dressed up for the party as cowpox.

Polio vaccines are made from viable genetic material from polio viruses grown in a lab, then fractured in their shell (protein or lipid hard shell) and the broken bits contain natural genetic markers for an immune response but the genetic material can't insert itself thru the outer cell wall of your cells. It's kinda like polio just shows it's Drivers license or ID to the cops which are your immune cells. The cops then are always on patrol to catch the bad guys.