The Covid-19 virus, like the HIV virus, may be able upload its RNA sequence into human DNA with the help of Reverse Transcriptase (RT) enzymes. Then the body's own DNA could generate Covid-19's viral genome sequence. (Human DNA could then generate Covid-19 RNA).
Note that Covid-19 does not contain the HIV virus, but it is believed to contain fragments of the HIV, which signal the presence of RT (reverse transcriptase).
That in itself is significant cause for further study.
There is additional concern that the Covid mRNA vaccines, in the presence of those viral RT enzymes (if present), could then enable the vaccine's own mRNA to upload a copy of its 'recipe' for one spike protein into the DNA.
This process could effectively replace the body's natural capacity to generate a wide variety of spike proteins to address diverse pathogens with the vaccine mRNA's limited capacity to produce one, predefined spike protein. This new 'recipe' for mRNA, transcribed by DNA, would be expected to be more stable and outcompete the body's original mRNA.