Now that the experts pronounced their judgement, it's worth to remember those words, "never say never again". mRNA vaccines are based on massive infusion of certain very specific messenger RNA into body cells. The process of recombination of DNA and RNA is in principle, possible and has been described. No, it has not been reported, to my knowledge, specifically in relation to Covid mRNA vaccines. But is a year of trials, under strong incentives and pressure to get to the market sufficient to assure that it cannot and will not ever happen? I'm not calling for it, but the Nature has been known for playing ironic tricks on over-confident scientists.