"Some people wonder whether the vaccines made using human fetal cells (chickenpox, rubella, hepatitis A, one version of the rabies vaccine, and one version of the COVID-19 vaccine) could cause harm if the DNA from the fetal cells “mixes” with the vaccine recipient’s DNA. This is not likely to happen: *Stability of DNA - Because DNA is not stable when exposed to certain chemicals, much of it is destroyed in the process of making the vaccine. Therefore, the amount of human DNA in the final vaccine preparation is minimal (trillionths of a gram) and highly fragmented. Because the DNA is fragmented, it cannot possibly create a whole protein that could be harmful. *Opportunity – DNA from the vaccine is not able to incorporate itself into cellular DNA. In fact, if this could be accomplished, gene therapy would be much easier than it has been."