As I understand it, immunity does not so much wane, as the virus evolves to evade it.

SARS-CoV-2 is a coronavirus. It’s the same family as the common cold. Viruses in that family mutate their surface antigens rapidly. That’s why we keep catching colds. We encounter an unfamiliar strain.

It’s also why we have annual flu shots. There are many varieties of flu viruses.

Natural immunity is not guaranteed to be superior to a vaccine. The vaccine can emphasize parts of the virus which mutate infrequently.

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