To the sibling commenters here: "traditional vaccines" are much more than killed-off viruses. They can be made of manufactured sub-units of viral proteins for e

To the sibling commenters here: "traditional vaccines" are much more than killed-off viruses. They can be made of manufactured sub-units of viral proteins for example. There has been continuous development of vaccines ever since the first ones were developed. In general, the problem is not getting (parts) of the virus into the body. This can for sure be done in many many ways. It's getting the immune system to care enough to start manufacturing and remembering the antibody formulae for future infections. One traditional way is to add an "adjuvant" to the viral subunits (or similar), which is designed to trigger the immune system. In either case, usually you do require to trigger some kind of local inflammation. When your arm hurts after a vaccine injection it's a good thing.