It looks like someone finally did the study I asked for many times. Why this was not done _before_ rolling out vaccines, I would love to know, since it's the very first thing I asked for when looking for research :(https://twitter.com/joshux321/status/1407591307598438402 …
There is a tangential explanation of why this paper is interesting here: https://blogs.sciencemag.org/pipeline/archives/2021/06/15/the-novavax-vaccine-data-and-spike-proteins-in-general … But generally speaking, the paper means we have some interesting questions still to answer about what exactly happens to spike proteins after manufacture.