If you aren't from these states, it gets a whole lot trickier. The 15-year-old boy from Minnesota was even desperate enough to ask if he should forge one of his parent's signatures (the answer is an emphatic no, forgery carries a $5,000 fine or up to 3 years in jail).
With no other legal way to get vaccines, your best bet is to convince your parents to give consent, even bringing in other adults to help with your argument if need be.
"I would recommend talking with a school nurse," one Redditor writes.
"They will be the most effective person to take up this fight against your mother, especially if there are immunizations you have yet to receive that are required for public school. A colleague of mine is a school nurse; believe me when I say that the good ones will fight tooth and nail with the anti-vaxxers."
"Agreed," another writes.
"My mom is a school nurse and has been dealing with a slew of anti-vaxxer parents over the last few years. She does a pretty good job of scaring or guilting the bejeezus out of parents to get their kids vaccinated."
Vaxopedia has a good list of resources for convincing your parents to give consent.
If that doesn't work, you can get vaccinated as an adult. Reddit is flooded with posts from adults who didn't receive their vaccines as a child for a reason.
If you do wait it out until you are old enough to consent, it's as simple as going to your doctor and telling them you are unvaccinated. They will tell you what vaccines you need and get you booked in.