Utah and Tennessee passed laws requiring foods containing vaccines to be classified as drugs, even though no such foods are on the market. Legislators pointed to a University of California study that is investigating whether it is possible to put vaccines in lettuce.

“You eat a bunch of this lettuce, take a bunch of these mRNA vaccines, and you go back and get your DNA tested again, it’s going to be a little different, it’s not going to be the same as it was that you were born with, that you got from your parents,” Frank Niceley, a Tennessee Republican state senator, said during the debate last year, arguing that the legislature should ban mRNA entirely. “This is dangerous stuff.”

In fact, mRNA vaccines cannot change the genetic code, because they cannot access the nucleus of the cells, where DNA resides. Small amounts of DNA are in all vaccines — often, as with the flu vaccine, because they are made from eggs — but the Food and Drug Administration enforces strict limits, and the levels are so small that they are negligible. Scientists had been conducting clinical trials on mRNA vaccines against infectious diseases and cancer for years, well before Covid: on mice in the 1990s and in humans starting in the early 2000s. While no vaccine is without side effects, including deadly ones, the mRNA vaccines often have fewer side effects than traditional vaccines that insert a small amount of live virus.

“mRNA is not some foreign substance, it’s something that you’re exposed to all the time,” said Melissa Moore, who was chief scientific officer at Moderna when it produced the Covid vaccines. “Every time you’re eating whole foods, meat or vegetables, you are consuming lots of mRNA and your body is breaking it down and creating its own.”

Even if the bills do not pass, their proponents say they are playing a long game. Last month, Republicans in Minnesota proposed a ban that would classify mRNA products as weapons of mass destruction, adding it to a list that includes smallpox, anthrax and mustard gas. The ban copied the language of a bill written by a Florida hypnotist, Joseph Sansone, who says he wants to try to get the ban passed in every state and in Congress. In his newsletter, Mr. Sansone praised local Republican organizations that have adopted resolutions in favor of the bans, and encouraged his followers to start showing up at political events to challenge politicians.

It’s “poking them in the eye,” he wrote, “which has an important psychological effect.”