Our DS is 7 yo & unvaxed. He was BF til 26 mos - self weaned. We take a lot of extra C, D & B complex.
I homeschool but he's still takes this lesson & in activites. We're much healthier as a whole than the vaxing families.
My son was partially vaxed up to 6 months then I stopped them completely. He nursed until he was two, and then he weaned himself when I got pregnant with his sister. His sister is now 2, no vaxes at all, and still...nurses from time to time. She'll sit on my lap and say "I turtee," (aka I'm thirsty). I would have done it even if I had vaxed them....child-led weaning. I think it does help, though, that they are rarely sick like many other kids and I feel the extended breastfeeding definitely helped them. Of course even some EBF kids, or any length of BM kids, can get sick a lot as well so it's not a blanket statement but it is a gut feeling on my part.
DS 1 nursed for 2.5 years, though he did receive some vaxes. DS 2 is still EBF at 7 months, and I plan to let him go as long as he likes, or until about 2.5 or so, and definitely some of the reasons we're EBF rather than starting any solids is the vax thing with DS2. DS1 is 5 now, and I can count on my fingers the number of times he's been seriously ill. I do attribute a lot of that to the extended BFing, though I think some has to do with good genes, good hygiene, and good luck.