From personal experience, I could count the number of times I'd been sick on one hand prior to joining the US Navy in 1993. When we got our round of vaccines in boot camp, I became very ill (I toughed it out and made it
through, but I was the walking dead for the 8.5 weeks I was there; had nausea and fever practically every day).
Ever since, I have had some pretty serious health problems: headaches (migraines and others), severe sinus problems, intermittent weight gain/loss, problems sleeping (or staying awake, depending), memory loss, etc.
Again, I had had nothing more than a cold in my whole life prior to 1993 (and very few of those), and after that first week of boot camp, it has been kinda rotten. I don't have any scientific evidence that proves the vaccines they gave me were the cause, but it doesn't take a genius to look at the timing and put two and two together...