By Daniel Dale, CNN(CNN) — President Donald Trump made numerous false or misleading claims about vaccines and autism on Monday. Trump again floated the idea that vaccines cause autism, though that notion has been thoroughly debunked by extensive research in multiple countries. Studies have debunked the idea of a link between vaccines and autismTrump did not explicitly assert that there is a connection between vaccines and autism. The notion of a connection between the measles, mumps and rubella (MMR) vaccine and autism was popularized by a fraudulent, debunked study in the 1990s. The MMR vaccine, to cite a typical example, has a dosage of 0.5 milliliters, roughly a tenth of a teaspoon.