Anthony Mundine has admitted he was "too fired up" when he encouraged parents not to vaccinate their kids.
The former boxer from Blakehurst posted a controversial anti-vaccination rant on Twitter, telling his followers "don't vaccine (sic) your kids period!"
"The government bully you into vaccine! Do your research on the s***," he wrote.
"All I'm saying is research and check what they giving you or ya baby!
"When they start mixing it like a cocktail that's where it's going wrong!"
But after he was condemned by hundreds online, including prominent Australians, he toned down his message.
"I probably was too fired up when I posted that first post. All parents ultimately want what is best for their kids!" he wrote on Thursday afternoon.
"Like I said in my last post, do your own research! Where there is risk, there must always be choice! I AM FOR informed consent and freedom of choice when it comes to all medical procedures."
The Australian Academy of Science responded to Mundine's latest comments with a link to a video titled "Immunisation saves lives".
The non profit organisation said they aimed to support people to make good health decisions based on science.
His first comments were criticised by paralympian and disability advocate Kurt Fearnley for promoting apathy over diseases that should be feared.
"You got many mates with Polio? I do. A heap. From countries that didn't have the luxury of vaccinations you peanut," the paralympic champion wrote.
Fearnley said it was "bad faith" for anti-vaxxers to say do your research when medical professionals had already done so.
"So do your research.. Consult your GP. Not Dr Google."
Prominent indigenous activist and academic Marcia Langton also hit back.
Professor Langton holds the Foundation Chair in Australian Indigenous Studies at the Melbourne University Faculty of Medicine.
"The science is in. Everyone must be vaccinated. Measles can kill and cause lifetime disabilities," she wrote.
The comments come a month after a study found no link between autism and the mumps, measles and rubella vaccine.
Anti-vaxxers have long claimed the MMR vaccine can cause autism, but researchers who studied more than half-a-million babies born in Denmark over 11 years found there is absolutely no association in a study released in March.
The federal government has launched a national television advertising blitz to counter the misinformation spread by anti-vaccination campaigners.
The federal government committed in February an extra $12 million over the next three years to reinforce the health benefits of the nation's immunisation program.