Jenny McCarthy got a big boost from her in the beginning of her antivax crusade too:

Of course, the notion that vaccines cause autism has never been supported by science. But Oprah gave McCarthy a vast audience via her TV show in 2007.Science journalist Seth Mnookin, who covered this meeting of the minds in his book The Panic Virus, reported that Winfrey “praised McCarthy’s unwillingness to bow to authority, her faith in herself, and her use of the Internet as a tool for bypassing society’s traditional gatekeepers.” Here’s an excerpt from the interview transcript:

MCCARTHY: First thing I did — Google. I put in autism. And I started my research.

WINFREY: Thank God for Google.

MCCARTHY: I’m telling you.

WINFREY: Thank God for Google.

MCCARTHY: The University of Google is where I got my degree from. … And I put in autism and something came up that changed my life, that led me on this road to recovery, which said autism — it was in the corner of the screen — is reversible and treatable. And I said, What?! That has to be an ad for a hocus-pocus thing, because if autism is reversible and treatable, well, then it would be on Oprah.

Days after that Oprah appearance, McCarthy was invited on Larry King Live and Good Morning America to spread her anti-vaccine message even further. Between the three shows, she reached between 15 million and 20 million viewers with her anti-vaccine message, Mnookin estimated.

To this day, the episode featuring McCarthy, “Mothers Battle Autism,” is featured on Oprah’s website, without any correction or acknowledgment of the problems with McCarthy’s claims.

https://www.vox.com/science-and-health/2018/1/9/16868216/oprah-winfrey-pseudoscience