A very good point. This is what my former physician's office (affiliated with a large hospital system) advises about the covid vaccines, straight from their website's FAQ section. "The Pfizer vaccine and the Moderna vaccine use mRNA to instruct the cells in your body to make a harmless piece of the “spike protein” found on the surface of COVID-19. Your immune system is tricked into thinking this is a virus and makes antibodies. A live virus is not included in the vaccine. Your body destroys the mRNA and gets rid of it. It doesn’t stay in your body or alter any DNA. The other ingredients in the Pfizer and Moderna vaccines are salt, sugar, and fat."