On the CDC's web site, "Myths and Facts about COVID-19 Vaccines" they say:
"FACT: COVID-19 vaccines do not change or interact with your DNA in any way."
"The genetic material delivered by mRNA vaccines never enters the nucleus of your cells, which is where your DNA is kept."
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/facts.html
But this study showed that the Pfizer vaccine can be converted into DNA in the nucleus of liver cells:
https://www.mdpi.com/1467-3045/44/3/73/htm
Immunohistochemistry using antibody binding to LINE-1 open reading frame-1 RNA-binding protein (ORFp1) on Huh7 cells treated with BNT162b2 (Pfizer vaccine) indicated increased nucleus distribution of LINE-1. PCR on genomic DNA of Huh7 cells exposed to BNT162b2 amplified the DNA sequence unique to BNT162b2.
Our results indicate a fast up-take of BNT162b2 into human liver cell line Huh7, leading to changes in LINE-1 expression and distribution. We also show that BNT162b2 mRNA is reverse transcribed intracellularly into DNA in as fast as 6 h upon BNT162b2 exposure.
5. Conclusions
Our study is the first in vitro study on the effect of COVID-19 mRNA vaccine BNT162b2 on human liver cell line. We present evidence on fast entry of BNT162b2 into the cells and subsequent intracellular reverse transcription of BNT162b2 mRNA into DNA.