Ethan Lindenberger from Ohio asked social media site Reddit if he could have vaccines without parental consent.
His mother would not give her permission, he wrote in the post, which had thousands of reactions.
He learned he had to wait until he was 18 – which he did, and has now had five vaccinations so far.
However, he told the BBC his mother still does not agree with his choice, and also apologised for the way he described her online.
“When I went on Reddit I expressed a lot of displeasure with my mum, I didn’t think it would go anywhere, I thought my mum was irrational, I was upset and I said some things I shouldn’t have,” he said on BBC World Service radio programme OS.
“I had to apologise for some of the stuff I said on Reddit, where I said she was irrational, crazy, dumb – because I was upset, I didn’t expect to be in the public eye and having to protect my mum. It’s not fair to her… she has done her own research.”
He added that his words had been “used against him” on social media.
“Anything you put online will become a weapon, if you don’t choose your words very carefully,” he said.
Mr Lindenberger added that he had stopped responding to online comments and criticisms.
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Referring to the vaccinations, he said he had never wanted to do anything behind his mother’s back, but had become convinced that it was the best choice for him and those around him.
“If I get whooping cough I may be able to handle it because I’m older and I have a good immune system, but who’s to say I don’t cough on my two-year-old sister?” he asked.
“That’s an extremely scary thought.”
One of his mother’s fears is that vaccinations may cause autism – although Andrew Wakefield’s 1998 paper linking the two has since been discredited.
“She believed very wholeheartedly that vaccinations cause these bad side effects,” Mr Lindenberg said.
“As I grew up I saw there was a large debate when she would share things online. I saw a lot of people disagreed with her.”
Mr Lindenberger added that his younger brother told him that he would also like to have the vaccinations, but is not yet old enough to make the decision for himself.