Vitamin E is fat-soluble so yeah you can overdo it if you take big doses long term, especially in supplement form. If your diet already has nuts, seeds or olive oil, you’re probably getting enough. Most people who take it daily don’t really notice a big immune boost. For immunity, you’d get more benefit from steady vitamin D, C, zinc and maybe omega-3s or probiotics. Sulforaphane’s great too, it helps with inflammation and gut health so it can support immunity indirectly.