Acute Corneal Transplant Rejection; declining vision of 2-day duration on the operated eye.; This literature-non-study case was reported in a literature article and describes the occurrence of CORNEAL GRAFT REJECTION (Acute Corneal Transplant Rejection) in a 61-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.   The patient's past medical history included Keratoplasty (Patient had contact lens related Aspergillus keratitis 3 years ago, requiring tectonic sclerokeratoplasty of the superotemporal quadrant followed 6 months later by optical penetrating keratoplasty (PKP) with extracapsular cataract extraction and posterior chamber intraocular lens placement.).   On an unknown date, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 1. On an unknown date, received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 1. On an unknown date, the patient experienced CORNEAL GRAFT REJECTION (Acute Corneal Transplant Rejection) (seriousness criterion medically significant) and VISUAL IMPAIRMENT (declining vision of 2-day duration on the operated eye.). The patient was treated with PREDNISOLONE ACETATE for Cystoid macular edema, at a dose of UNK UNK, qd. At the time of the report, CORNEAL GRAFT REJECTION (Acute Corneal Transplant Rejection) and VISUAL IMPAIRMENT (declining vision of 2-day duration on the operated eye.) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Corneal pachymetry: cct measured 752 um). CCT measured 752 um). and decreased CCT decreased to 610 mm. On an unknown date, Slit-lamp examination: slitlamp examination revealed mild conjunctival in Slitlamp examination revealed mild conjunctival inflammation, a corneal endothelial rejection line with fresh KP. On an unknown date, Visual acuity tests: normal BCVA returned to 20/40 with a clear compact cornea graft devoid of neovascularization, bcva was reduced to 20/80 BCVA was reduced to 20/80 and increased vision improved to 20/60.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown Route), the reporter considered CORNEAL GRAFT REJECTION (Acute Corneal Transplant Rejection) and VISUAL IMPAIRMENT (declining vision of 2-day duration on the operated eye.) to be possibly related.    This case concern 2 out of 4 patients with prior keratoplasty developed presumed immunologic rejection after the mRNA-1273 vaccination for coronavirus 2 (SARS-CoV-2). One year before current presentation, accidental blunt trauma resulted in limited keratoplasty wound dehiscence with uneventful repair.  The patient received the first dose of the mRNA-1273 COVID-19 vaccine (Moderna) without incident and, accordingly, 4 weeks later received the second vaccine dose. She presented 1 week later complaining of declining vision of 2-day duration on the operated eye. Prednisolone acetate 1% was increased to hourly frequency, and on this regimen, at 6-week follow-up, vision improved to 20/60, with resolution of conjunctival inflammation, KPs, and endothelial rejection line. Topical steroids were tapered to prednisolone acetate 1% 4 times daily.  These cases suggest acute corneal endothelial rejection may occur soon after either dose of the COVID-19 mRNA vaccine. Prompt initiation of aggressive topical steroid therapy may result in complete resolution of clinical signs and symptoms. Further studies are needed to elucidate the causal mechanism of corneal graft rejection after COVID-19 vaccination.   This case concerns a 61-year-old, female patient with medical history of keratoplasty with extracapsular cataract extraction and posterior chamber intraocular lens placement 3 years ago, and subsequent keratoplasty wound dehiscence after a accidental blunt trauma with clear compact cornea graft placement a year ago,  who experienced the unexpected serious event of corneal graft rejection together with non-serious unexpected event of visual impairment. The event of corneal graft rejection occurred approximately 1 week after the first dose of Spikevax (Moderna COVID-19 vaccine; according to narrative, with administration date unknown). The rechallenge was not applicable since the event occurred after the second dose. The event was considered related to the vaccine per the re   This case was linked to MOD-2021-349123, MOD-2021-353544, MOD-2021-353542 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 13-Oct-2021: Follow up received by safety 14-Oct-2021 has Email contain new information about patient identifier.; Sender's Comments: This case concerns a 61-year-old, female patient with medical history of keratoplasty with extracapsular cataract extraction and posterior chamber intraocular lens placement 3 years ago, and subsequent keratoplasty wound dehiscence after a accidental blunt trauma with clear compact cornea graft placement a year ago,  who experienced the unexpected serious event of corneal graft rejection together with non-serious unexpected event of visual impairment. The event of corneal graft rejection occurred approximately 1 week after the first dose of Spikevax (Moderna COVID-19 vaccine; according to narrative, with administration date unknown). The rechallenge was not applicable since the event occurred after the second dose. The event was considered related to the vaccine per the reporter's assessment. The medical history of previous intra-ocular surgery and the time since graft placement (with most rejections occurring one year after surgery, coinciding with latency in this case), could be confounders to corneal graft rejection. The benefit-risk relationship of Spikevax (Moderna COVID-19 vaccine) is not affected by this report.