It's the most ridiculous myth used to scare parents.

There’s a mum from my playgroup who feels guilty because of it.

I can never forget this mum. She came to playgroup with her son, who was a bit older than my daughter. He walked around the hall on his own. She told me he’d been diagnosed as autistic.

She told me he’d got autism from a vaccine.

Her husband had told her not to get their baby boy vaccinated, but while he was away, she’d done it. Now her son had autism. I could see the pain in her face. I could see she’d been living with the guilt for years.

“But vaccines don’t cause autism,” I told her.

She was sure they did. She started talking about vaccines containing mercury and all sorts of other things. I didn’t have the scientific facts at my fingertips to reason with her. I wasn’t expecting this kind of debate at playgroup.

She went home with her son. I never saw her again.

I wish I could see her now. In the five years since I talked to her, I have learnt a bit about vaccines. The ones given to kids in Australia don’t contain mercury. As for the false belief that the measles/mumps/rubella vaccine causes autism, that stemmed from “research” by a British doctor called Andrew Wakefield. That “research” has been exposed as a fraud. Andrew Wakefield has been found guilty of serious professional misconduct and barred from practising medicine in the UK. A huge amount of genuine research has proven there is no link between vaccines and autism.

And yet that false belief is still being spread.

A little while back, I talked to a man in the US called John Salamone. More than 20 years ago, his son David contracted polio from a polio vaccine. Back then, polio vaccines were "live" vaccines, and there was a one in 2.4 million chance that a baby given the vaccine would contract polio. David was one of the very unlucky ones. Because of families like the Salamones, the US switched over to an "inactive" vaccine, and Australia did the same. That's right. The government accepted that a one in 2.4 million risk of a child contracting polio from a vaccine was just too much. (By the way, John and his family are pro-vaccine.)

Do people really think the government would be encouraging parents to get their kids vaccinated if there was evidence that vaccines caused autism? I mean, seriously? Why?

Do people really think that all the doctors and nurses who promote and run the childhood immunisation program are stupid? Or do they honestly believe that these doctors and nurses, who we trust with our health at all other times, are involved in some kind of evil conspiracy?

Vaccination saves kids' lives. It's as simple as that. We do it to protect our kids, and to protect other people's kids who are not as big and strong and healthy as our own. And yet New South Wales has had to introduce a "no jab, no play" policy at childcare centres, because so many parents aren't vaccinating their children. Now Victoria is going to do the same.

We should not be wasting time and energy having a "debate" on whether childhood immunisation is a good thing. Kids in Australia should not be dying from preventable diseases. And no one should have to live with the guilt that they gave their child autism.

To the playgroup mum, I hope you have found out the truth. You did not give your son autism. You did the right thing by getting him vaccinated.

Have you got into debates about vaccination with other mums?

Want more? Try:

The amazing lesson my daughter with autism taught me.

Ryder's mum: "We weren't aware of the vaccine that might have saved him."

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