Menstrual bleeding got heavier/the patient usually have regular cycles, was not sexually active for the past 6 months and does not have any IUDs; Spotting; Periods out of whack; Menstrual cramps; Injection site redness; Injection site swelling; Injection site itching; Injection site rash; This spontaneous case was reported by a nurse and describes the occurrence of INTERMENSTRUAL BLEEDING (Spotting), MENSTRUAL DISORDER (Periods out of whack), DYSMENORRHOEA (Menstrual cramps), HEAVY MENSTRUAL BLEEDING (Menstrual bleeding got heavier/the patient usually have regular cycles, was not sexually active for the past 6 months and does not have any IUDs) and VACCINATION SITE ERYTHEMA (Injection site redness) in a 36-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 300042460) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Penicillin allergy and Drug allergy (Clindamycin allergy.).    On 04-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 04-Jan-2021, the patient experienced VACCINATION SITE ERYTHEMA (Injection site redness), VACCINATION SITE SWELLING (Injection site swelling), VACCINATION SITE PRURITUS (Injection site itching) and VACCINATION SITE RASH (Injection site rash). On 06-Jan-2021, the patient experienced MENSTRUAL DISORDER (Periods out of whack) and DYSMENORRHOEA (Menstrual cramps). On 09-Jan-2021, the patient experienced INTERMENSTRUAL BLEEDING (Spotting). On 10-Jan-2021, the patient experienced HEAVY MENSTRUAL BLEEDING (Menstrual bleeding got heavier/the patient usually have regular cycles, was not sexually active for the past 6 months and does not have any IUDs). The patient was treated with IBUPROFEN (ADVIL [IBUPROFEN]) for Adverse event, at an unspecified dose and frequency; DIPHENHYDRAMINE HYDROCHLORIDE (BENADRYL [DIPHENHYDRAMINE HYDROCHLORIDE]) for Adverse event, at an unspecified dose and frequency and HYDROCORTISONE for Adverse event, at an unspecified dose and frequency. On 11-Jan-2021, HEAVY MENSTRUAL BLEEDING (Menstrual bleeding got heavier/the patient usually have regular cycles, was not sexually active for the past 6 months and does not have any IUDs) had resolved. On 13-Jan-2021, INTERMENSTRUAL BLEEDING (Spotting) had resolved. At the time of the report, MENSTRUAL DISORDER (Periods out of whack) and DYSMENORRHOEA (Menstrual cramps) outcome was unknown and VACCINATION SITE ERYTHEMA (Injection site redness), VACCINATION SITE SWELLING (Injection site swelling), VACCINATION SITE PRURITUS (Injection site itching) and VACCINATION SITE RASH (Injection site rash) was resolving.        The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   No Concomitant were medications reported.  On 6JAN2021, she started getting cramps. She started spotting  On 9JAN2021 and on 10JAN2021, the bleeding got heavier. On 11JAN2021 her period got lighter and she has continued to have spotting until 13JAN2021. Patient reports she is not sexually active and has not been since the last 6 months. She is usually on time with her cycles and was not supposed to get her period until 24JAN2021. She does not have any IUDs.   This case was linked to US-MODERNATX, INC.-MOD-2021-005884 (E2B Linked Report).   Most recent FOLLOW-UP information incorporated above includes: On 04-Jun-2021; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded. US-MODERNATX, INC.-MOD-2021-005884: