Complex sentence: No medical basis for this immunity is identified in the research conducted, nor is it discovered why those who have immunity are immune; the only evident connection between immune persons that doctors identify is that all seem to be heavy, vivid dreamers.
Split into simpler sentences: No medical basis for this immunity is identified in the research conducted, nor is it discovered why some people have immunity. The only evident connection between the immune persons that doctors identify is that all seem to be heavy, vivid dreamers.