While it is not proven it has been theorized that downs syndrome was actually caused by the first vaccines.  This is entirely possible timeline wise.  Jenner’s smallpox vaccine 1798, Downs syndrome was identified in 1866. (of course it could just have been broader diagnostic criteria and better trained doctors) LOL  Downs syndrome is caused by an extra (3rd)  21st chromosome and affects about 1 in every 800 children.   If it is actually true that the first vaccines are responsible for downs syndrome think about the implications.  Vaccines would be capable of changing the human genetic code.