These celebrities are not doctors. So let's not listen to them about vaccinations.

We repeat: These celebrities are not doctors. Is that clear enough?

In the face of a measles epidemic, Barack Obama has changed his once-controversial views of vaccines. Yes, that’s right. Obama was once an anti-vaxxer.

As measles continue to sweep across the US, President Barack Obama has urged all parents to have their children vaccinated, saying the science is “indisputable”.

“There is every reason to get vaccinated, there aren’t reasons to not,” Obama said in an interview with the Today Show last Tuesday.

Obama confirmed that both his children, Sasha and Malia, had been vaccinated — and urged other parents to do the same for their kids because “it’s good for them”.

Read more: This is why you need to immunise your children.

“We should be able to get back to the point where measles effectively is not existing in this country,” the President told interviewer Savannah Guthrie. “We’ve studied this a lot. And the fact is that a major success of our civilization is our ability to prevent disease.

“The science is, you know, pretty indisputable. We’ve looked at this again and again,” Obama went on. “There is every reason to get vaccinated, but there aren’t reasons to not.”

Right on, Obama.

But in news that left us gobsmacked, it turns out the US President wasn’t always such a staunch pro-vaccine advocate. No, we’re not kidding: In 2008, Obama, as a senator and presidential candidate at the time, made a statement that him sound suspiciously like an anti-vaxxer.

In April 2008 — eight months before assuming office — Obama called the science around the so-called “link” between autism and vaccines “inconclusive”, as Politico reports.

“The science right now is inconclusive, but we have to research it,” he said.

Related content: Hillary Clinton just sent out an excellent pro-vaccine tweet.

The “link”, of course, has never been supported by science. In fact, a huge Danish study examined 537,303 children, and found there was no association between vaccination and the development of autistic disorder.

In 2004, the Institute of Medicine again rejected claims that thimersoral, an agent commonly found in vaccinations, could cause autism. Last year, yet another study by the University of Sydney looked at data involving more than 1.25 million children — and conclusively found that there is no link between vaccination and the development of autism, or autism spectrum disorders.

We’ll say that again: Science says there is No. Link. Between. Vaccines. And. Autism.

Despite that fact, Obama is certainly not the only influential American who’s espoused some pretty troubling views on vaccines. Today, we bring you a list of some of the most influential figures who’ve aired (or provided a platform for) some troubling anti-vaxxer views…

Oprah Winfrey.

Okay, all the evidence suggests Oprah’s no anti-vaxxer herself. But, as the Daily Beast reports, the 61-year-old talk show host certainly gave a powerful platform to outspoken anti-vaxxer Playboy Playmate Jenny McCarthy, who appeared on The Oprah Winfrey Show claiming a link between vaccines and autism.

“You’re mother warriors is what you are,” Oprah said in 2007, praising McCarthy for her dedication to fighting autism.

Donald Trump.

“You know, I have a theory (about the rise in autism diagnoses),” real estate magnate Trump, 68, said in an interview on Fox News. “And it’s a theory that some people believe in — and that’s the vaccinations. We never had anything like this. This is now an epidemic.”

Read more: Can parents sue anti-vaxxers for this measles epidemic? 

Jim Carrey.

“If we are to believe that the ruling of the ‘vaccine court’ in these cases mean that all vaccines are safe, then we must also consider the rulings of that same court in the Hannah Polling and Bailey Banks cases, which ruled vaccines were the cause of autism and therefore assume that all vaccines are unsafe,” actor Jim Carrey, 53, wrote for the Huffington Post. “Clearly both are irresponsible assumptions, and neither option is prudent.”

Alicia Silverstone

“While there has not been a conclusive study of the negative effects of such a rigorous one-size-fits-all, shoot-’em-up schedule, there is increasing anecdotal evidence from doctors who have gotten distressed phone calls from parents claiming their child was ‘never the same’ after receiving a vaccine,” 38-year-old Clueless star Alicia Silverstone wrote in her book The Kind Mama. “And I personally have friends whose babies were drastically affected in this way.”

Kristin Cavallari

“I understand both sides of it. I’ve read too many books about autism and there’s some scary statistics out there,” Laguna Beach star Cavallari, 28, said on Fox Business show The Independents. “It’s our personal choice, you know, and if you’re really concerned about your kid, then get them vaccinated and it shouldn’t be a problem.”

On that point, Kristin, we can agree.