It's obviously NOT a huge deal. The Daily Telegraph far right misinformation newspaper has twisted the report into misleading garbage.

Locate the original report, which notes the accurate information:

In collaboration with researchers at the Universities of Kent, Oxford and Liverpool, the MRC Toxicology Unit team tested for evidence of the production of ‘off-target’ proteins in people who received the mRNA Pfizer vaccine against COVID-19. They found an unintended immune response occurred in one third of the 21 patients in the study who were vaccinated – but with no ill-effects, in keeping with the extensive safety data available on these COVID-19 vaccines.

https://www.cam.ac.uk/research/news/researchers-redesign-future-mrna-therapeutics-to-prevent-potentially-harmful-immune-responses

1st) The sample group was ONLY 21 people, and the unintended response was so minor that there was no ill effect. That unintended response could be a temporary swelled arm, where the shot was given. There are numeroud possibilities. The important bit is that there were NO ILL EFFECTS.

2nd) Hence the next step is to do a proper study with larger sample groups and with the removal of uridine.

3rd) The purpose of that research was to fix a problematic non-essential nutrient, uridine, in the Phizer vaccine.

Connecting that research with what you note here is of course not reliable. You'd have to look at studies of uridine, and this is our only example at the moment. Any other assumption is pure guesswork.

Moreover - you're seeing in that report the very brief results of medical science research. Anti-vax groups claim that science and medical science research are false, and that only their anti-science mates on Twitter know through divine wisdom (or a paid fraud claiming to be an expert) how to understand virology and vaccines.