n95 masks and higher are highly effective at filtering virus, including corona. That's why medical professionals wear them. You are obviously better off avoiding sick people, but if you can't, masks are a critical safety precaution. Stop believing WHO and CDC propaganda which is intended to preserve the supply of masks for their staff, which they believe is critical to public health, but does you no good as an individual. There are dozens of studies showing the efficacy of masks. Google it.
https://www.newscientist.com/article/dn3692-face-masks-are-best-protection-against-sars/
Surgeons wear masks to prevent their spittle and large respiratory secretions from contaminating a surgical field. Sorry but as long as the seal is not complete 2-3 micron thick viruses enter. Put another way. Don’t bet your life that a face mask will preserve your health. Also the allure of pseudoscience is great. But there is absolutely no credible evidence that vitamins strengthen immune response.