Over the years, Donald Trump has claimed to be an authority on business and politics. Now? He thinks he’s a medical expert, too — and actual doctors are not amused.

“Massive combined inoculations to small children is the cause for big increase in autism,” Trump tweeted to his 1.4 million Twitter followers on Thursday. “Spread shots over long period and watch positive result.”

Trump was referring to the long-debated but medically-debunked theory that vaccinations can cause autism in children, an idea first espoused in a 1998 paper by Andrew Wakefield. Since then, numerous medical studies have proven it untrue, and the British Medical Journal even called it “fraudulent.”

The Donald’s silly grabs for attention are well-known, but this time, doctors felt the need to weigh in.

“The autism-vaccine link has been disproven,” said Dr. Richard Besser, the chief health and medical editor for ABC News. “Spreading shots out over a long period of time will not reduce the number of children who develop autism, but it will leave more children vulnerable to infectious diseases for a longer period of time than necessary.”

Dr. Besser went to call Trump’s claims “shameful,” and Twitter users agreed, with one saying, “You should be ashamed of yourself. Leave medicine to physicians.”

[ABC News]