acute kidney injury; gross hematuria/macroscopic hematuria; Proteinuria; stage I hypertension; This is a literature report from the Medical Journal. This Other Health Professional reported similar events for two patients. This is the second of two reports.  To the editor: With great interest, we read the recent reports of IgA nephropathy (IgAN) flare-up presenting as macroscopic hematuria, following the second dose of coronavirus disease 2019 (COVID-19) vaccination in adult patients. The Administration granted an emergency use authorization for the Pfizer-BioNtech COVID-19 vaccination in Dec2020 for individuals aged 16 years; the emergency use authorization was recently expanded to include children aged 12 to 15 years on 10May2021. Herein, we report 2 pediatric patients with IgAN presenting with macroscopic hematuria <24 hours after Pfizer COVID-19 vaccination. Neither patient had COVID-19 infection before vaccination nor any history of reactions to any vaccinations. The second patient is a previously healthy 17-year-old boy who presented with new-onset gross hematuria, proteinuria, and acute kidney injury <24 hours following the second dose of the vaccine. He had no family history of autoimmune disease, and he was not taking any medications. His gross hematuria self-resolved, but his kidney insufficiency persisted. Kidney biopsy performed 9 days later was consistent with IgAN with cellular glomerular crescents and moderate to severe tubulointerstitial scarring (IgAN with cellular glomerular crescents. Moderate interstitial fibrosis is evident on the trichrome stain. The glomerulus on the left shows a segmental cellular crescent, and the glomerulus on the right shows segmental mesangial hypercellularity with mild mesangial matrix expansion on periodic acid-Schiff stain. Immunofluorescence staining shows 2+ granular mesangial staining for IgA. Electron microscopy shows electron-dense deposits in mesangium), suggesting an acute exacerbation of preexisting IgAN. He received i.v. methylprednisolone pulses, and his follow-up serum creatinine level showed improvement. The mechanism by which COVID-19 vaccination may be associated with IgAN flares is unclear. We concur with previous authors statements that patients, including children, with IgAN should be monitored closely following COVID-19 vaccine, and COVID-19 vaccination may unmask previously undiagnosed glomerulonephritis in pediatric patients. Before COVID-19 vaccination: the patient had Foamy urine for several months. Following COVID-19 vaccination: New-onset macroscopic hematuria x 4 d and stage I hypertension. Variables: Serum creatinine mg/dl, Following COVID-19 vaccination: Day 6: 1.78, Day 9: 1.47, Day 22: 1.20 following corticosteroid treatment); Serum albumin g/dl Day 9: 3.8; Urine protein to creatinine ratio, mg/mg, Day 9: 1.75. Oxford MEST-C score Day 9: M1 E1 S1 T1 C1. Treatment for acute kidney injury included: Day 9: 1 g i.v. methylprednisolone daily x 3, followed by oral prednisone.; Sender's Comments: Based on the review of available information, the causal relationship between the adverse reaction Acute Kidney Injury (AKI) and the suspect product  Pfizer-BioNtech COVID-19 vaccination is assessed as possibly related.  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.,Linked Report(s) : 202101224115 Same article/ patient and different drug/event