mRNA vaccines do not do anything to the DNA of a human cell.
Posts on Facebook and other social media sites have been claiming that the Pfizer vaccine will change our DNA, "reprogramming" us and turning everyone who takes it into a "genetically altered" human being.
It would seem that those who post such claims misunderstand genetics. The Pfizer COVID-19 vaccine is an mRNA vaccine (or messenger RNA vaccine). According to the PHG Foundation, a health policy think tank, RNA vaccines work by introducing an mRNA sequence (the molecule which tells cells what to build) which is coded for a disease-specific antigen. Once produced within the body, the antigen is recognized by the immune system, preparing it to fight the real thing.
There are many advantages to mRNA vaccines, including the fact that they can be quick and cheap to develop. Real concerns center around the length of protection they offer, not whether they alter your DNA. Indeed, mRNA vaccines do not do anything to the DNA in a human cell. They just trigger an immune response by instructing the body's cells to produce the vaccine antigens.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.