My experience in this area is quite dated, I don't want to give the impression I'm truly an expert in this area. My guess- based on a few decades of working wi

My experience in this area is quite dated, I don't want to give the impression I'm truly an expert in this area. My guess- based on a few decades of working with DNA and RNA and proteins, is that it's unlikely a small amount of unintentional DNA in a vaccine would cause any detectable harm. The argument is basically that the DNA would have to have very specific sequence to be transcribed by DNA Polymerase to RNA, the resulting RNA would need to have a very specific sequence to be translated, and to avoid being detected as foreign RNA (cells have a robust collection of tools to dice up invading DNA). And I agree that the resulting proteins- even if through some extremely improbable event led to a small number of peptides or protein fragments were expressed, they would be "mopped up by the immune system", with some inflammation, as you say. Witha ll that said I'm sure you can find examples of people who set up cellular experiments that demonstrated some injected DNA could be expressed, as biology is ultimately a probabilistic and stochastic system and there's always some level of nonspecific behavior that can't be ruled out.