Yes there is - natural immunity is something you get from being exposed to a virus and having your immune system fight it off. Before vaccines, that is how everyone developed immunity.
Well, that was one part, unfortunately the other part of it was natural selection and selection of traits that were resistant. In other words: a lot of people died, some people developed some immunity directly and survived, some people had genetic mutations that proved beneficial to either resisting the virus directly or to helping the immune system handle it and survived, even if it could cause other problems (for example: the trait for sickle cell and it's relation to malaria). For both those components, as I said, a *lot* of people died along the way. We don't really want that to be our modern solution.
8 Catfish = 1 Octo-puss