21 days late, neg. pregnancy test, & meningitis vaccine

I am currently 21 days late. I took a pregnancy test a few days ago & it came out negative. I have had plenty of menstrual cramping & I'm pretty positive that I'm not pregnant. I have no signs or symptoms of pregnancy. A week before I was supposed to get my period, I was injected with the meningitis vaccine. I got really sick, because that vaccine has side affects. Could this vaccine have possibly affected my menstrual cycle?

I have no experience with this at all but this is exactly what i'm on here for. The same thing happned to my girlfriend and i'm trying to find out if it affected her cycle. I'm going to try and look up known side effects of the vaccine.