First of all, it's "unnatural", second, you seem to have misunderstood what "artificial" means in this context, it even explains in the Wikipedia article, that

First of all, it's "unnatural", second, you seem to have misunderstood what "artificial" means in this context, it even explains in the Wikipedia article, that it's external stimulation of existing immune response via vaccines and medication etc. Please do your research and read the articles before assuming.