MMR-vaccine and regression in autism spectrum disorders: negative results presented from Japan.

Japan stopped using the MMR shot in 1992. Tokio et al. used that break to ask a simple question.

They looked at kids who got the shot before the stop, kids who got it during, and kids born after. Then they counted how many lost skills.

The design is called a natural experiment. The country, not the scientists, decided who was exposed.

Regression rates stayed flat. Kids with autism lost words or play skills just as often in the no-shot years as in the shot years.

The shot did not push any child over a cliff.

Cheslack-Postava et al. (2021) did the same trick in Finland. They used blood cotinine instead of shot records. Moms who smoked more did not have more autistic kids. Both studies show the same flat line.

Tsujiguchi et al. (2023) looked at Japanese kids again, but for food, not shots. Kids with more autistic traits ate fewer vitamins. That paper and this one together paint Japan as a place where simple causes keep failing to show up.

Song et al. (2024) hunted inside the brain. They found no chemical gap in GABA or glutathione between autistic and typical kids. Tokio et al. found no outside trigger. Inside and outside, the null keeps repeating.

Parents still ask, “Did the shot do this?” You can now say, “Japan tried to prove it and got nothing.” Use the paper as a two-minute story. Show the graph of flat regression lines. Move the visit back to skills teaching, not blame hunting.