I agree with Dave Wright above...
DNA makes mRNA that makes proteins in the ribosome.
Thus mRNA does not change DNA as the process does not work in reverse.
The B vitamins may influence the process in other ways, but not through epigenetic methylation as that works only on the DNA.
The mRNA in the vaccine is not produced in the DNA. It’s synthetic. So the vaccine mRNA goes into the cells ribosomes to produce the spiked proteins and does not even enter the nucleus where the DNA is contained.
These spiked proteins act as antigens to trigger the immune response.
Thank you for the comments that helped me understand this...
RNA vaccines can be divided into traditional mRNA-based vaccines and self-amplifying mRNA (SAM) vaccines. Their basic principle is to use the host cell’s transcription system to produce target antigens to stimulate adaptive immunity.
The difference is that the former contains only the target antigen gene and cannot replicate itself; the latter encodes the engineered genome of the RNA virus, which contains the virus’s non-structural protein gene and the antigen gene that replaces the structural protein gene.
The resulting RNA can express antigenic genes at a high level due to the amplification effect of the RNA template, and these replicons cannot produce infectious virions because they delete the gene of the structural protein of the virus, and cannot spread to the adjacent cells.