Two days after this 8 year old received Dose #1 of the Pfizer Covid-19 vaccine, the patient started first menses (described as light brown/red bleeding x 4 days that required a light pad). The patient/parent consulted with their primary care provider given a concern it was related to the vaccine. A visit with PCP took place on 1/25/22.  Notes from that visit included: '8yo female here for early puberty with menstrual period 3 days after her Covid-19 vaccine. Growth charts and previous misc. charts from 2020 and 2021 reviewed. Rapid height growth between growth charts from 2020--2021 which strongly suggests pubertal onset during that time but family does not believe she had breast tissue at that time. There is not documented GU or breast exam at these visits. Pubertal development has progressed quite rapidly to menarche which typically takes on average 2-3 years. It is also atypical for such a significant time difference from maternal menarche. Case was discussed and reviewed at length with pediatric endocrinologist who recommend morning labs and BA as well as endo referral. DDX includes central (CNS, malformation, idiopathic) vs peripheral (CAH, adrenal, exogenous steroids, etc.) vs benign variant. I have not heard of any case reports of menarche onset from Covid 19 vaccine though there have been menstrual cycle changes in pubertal women. Precocious puberty and rapid progression clearly established prior to Covid-19 vaccine. Family requesting letter that completion of workup be performed prior to Covid-19 vaccine #2 which I think is reasonable and a letter has been provided to them stating this". On 2/2/22, the patient/parent had an office visit with a pediatric endocrinologist. That visit note describes the following: "She had her 1st dose of COVID vaccine on 1/6/2022 and a few days later, was noted to have light brownish red bleeding on her underwear, requiring light pads, which lasted for 4 days. No abdominal pain, no constipation, no dysuria. They saw Dr. for a follow up visit last week, and he consulted with me. Labs and bone age were ordered. Parents note that since summer of 2021, she started growing very fast. She also had onset of breast tissue for at least 1 year, and a few months ago started to have pubic hair. No axillary hair. She has been complaining of lower leg pain. She always has been a good eater, a increase in appetite lately. Denies fatigue, headaches, vision concerns. Eye exam normal recently. Parent denies that the child has any exposure to hormones, herbal products, tea tree oil, or lavender products. Patient does not have any headaches or visual changes. No abdominal pain, joint pain or birth marks. Growth chart shows that patient has had an increased growth rate. Weight was previously around 65% at 4-6 yrs, 74% at 7 yrs, 94% at 8 yrs 4 months and now at 95%. Height was around 50-60% till 7 yrs, jumped to 91% at 8 yrs 4 months and now 96%". Overall, patient diagnosed with central precocious puberty, supported by physical exam and biochemical testing. Parents have elected to see if patient has another episode of bleeding before making a decision about treatment with a GnRH agonist injection. VAERS completed. Parents also asked for information on the Countermeasures Injury Compensation Program.