HI, Nither Mondeslor nor vaccinations have any effect on menses. the abdomen & back pain you have may be pre menstrual symptom, still you need to investigate for absence of periods for 2 months. - First possibility in your age is Pregnancy,If you had unprotected sex , you can go for urine /blood pregnancy tests , to know the situation. - In absence of pregncy you need to investigate for the absence of menses.- right from routine blood work & hormonal assessment to ultrasound check up- various investigations are done after a physical examination ,as per need. -A general debility ( probably due to severe asthama attack), hormonal disturbances are known to cause absence of menses ,like you have. I would advice you to consult a Gynecologist for a specific guidance after diagnosis. Thanks