It's easy to find papers discussing the problem, just search Google Scholar. Example:
https://bpspubs.onlinelibrary.wiley.com/doi/full/10.1002/prp...
Integration was proven in 2024, unfortunately :(
https://www.medrxiv.org/content/10.1101/2024.03.24.24304286v...
"Of the S1 positive post-vaccination patients, we demonstrated by liquid chromatography/ mass spectrometry that these CD16+ cells from post-vaccination patients from all 4 vaccine manufacturers contained S1, S1 mutant and S2 peptide sequences"
They can tell the difference between vaccine spike and virus spike as the vaccine spike was modified for stability. The exact pathway is speculated to have been DNA contamination due to manufacturing process defects. Sequencing of vaccine vials has shown far higher levels of DNA contamination than is considered safe, and the lipids would bring DNA into the cells just as well as they do mRNA making the safe levels much lower still.
https://www.medrxiv.org/content/10.1101/2024.03.24.24304286v...
But yes further study has to be made.