After my second dose I had extremely heavy bleeding; Change in menstrual cycle every month after second dose; cramping; I am having heavy periods that are lasting 8-17 days./My last period (Nov2021) was not as heavy but still abnormally long; This is a spontaneous report received from a contactable reporter nurse. The reporter is the patient. A 26 year-old female patient (not pregnant) received bnt162b2 (PFIZER-BIONTECH COVID-19 VACCINE), administered in arm right, administration date 19May2021 16:00 (Lot number: EW0178) at the age of 26 years as dose 2, single for covid-19 immunisation. Relevant medical history included: "Migraines" (unspecified if ongoing); "asthma" (unspecified if ongoing); "ADHD" (unspecified if ongoing); "Known allergies: Dust" (unspecified if ongoing); "Known allergies: Seasonal allergies" (unspecified if ongoing); "Known allergies: Pet Dander" (unspecified if ongoing); "I have an IUD" (unspecified if ongoing), notes: IUD had been in place for 1.5 years and was not dislodged. No other vaccine in four weeks. Concomitant medications included: ALBUTEROL [SALBUTAMOL]. Vaccination history included: Bnt162b2 (Dose Number: 1, Lot No: EW0158, Location of injection: Arm Right, Vaccine Administration Time: 12:00 PM), administration date: 28Apr2021, when the patient was 26 years old, for Covid-19 Immunization. The following information was reported: HAEMORRHAGE (medically significant) with onset 23May2021 08:00, outcome "not recovered", described as "After my second dose I had extremely heavy bleeding"; MENSTRUAL DISORDER (non-serious) with onset 23May2021 08:00, outcome "not recovered", described as "Change in menstrual cycle every month after second dose"; MUSCLE SPASMS (non-serious) with onset 23May2021 08:00, outcome "not recovered", described as "cramping"; HEAVY MENSTRUAL BLEEDING (non-serious) with onset 23May2021 08:00, outcome "not recovered", described as "I am having heavy periods that are lasting 8-17 days./My last period (Nov2021) was not as heavy but still abnormally long". The events "after my second dose i had extremely heavy bleeding", "change in menstrual cycle every month after second dose", "cramping" and "i am having heavy periods that are lasting 8-17 days./my last period (nov2021) was not as heavy but still abnormally long" were evaluated at the physician office visit. Therapeutic measures were taken as a result of haemorrhage, menstrual disorder, muscle spasms, heavy menstrual bleeding. Clinical details as follows: Adverse event: Change in menstrual cycle every month after second dose. I have an IUD and have not had a period that required a tampon in over 4 years. After my second dose I had extremely heavy bleeding and cramping that made it difficult to perform daily tasks. I was seen by my primary care provider about this issue and we decided to monitor the issue. I rarely had a period more than 3 days but now I am having heavy periods that are lasting 8-17 days. No other medicinal history changes outside of the vaccine. IUD had been in place for 1.5 years and was not dislodged. My last period (Nov2021) was not as heavy but still abnormally long when comparing my menstrual history long term. My primary care provider has decided to abstain from getting the booster shot for this reason. Adverse event start date was 23May2021. Adverse event start time was 08:00 am. AE resulted in Doctor or other healthcare professional office/clinic visit. AE treatment was Assessment by primary care provider. No new meds. No covid prior vaccination. No covid tested post vaccination.