Acute Corneal Transplant Rejection; declining vision in the left 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 69-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. Concurrent medical conditions included Type 2 diabetes mellitus, Salzmann nodular degeneration and Fuchs' endothelial dystrophy.   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 in the left eye). The patient was treated with PREDNISOLONE ACETATE for Cystoid macular edema, at an unspecified dose and frequency and DIFLUPREDNATE for Cystoid macular edema, at an unspecified dose and frequency. At the time of the report, CORNEAL GRAFT REJECTION (Acute Corneal Transplant Rejection) and VISUAL IMPAIRMENT (declining vision in the left eye) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Ophthalmological examination: 719 micrometer 719 micrometer and increased 633 micrometer CCT 633 micrometer. On an unknown date, Slit-lamp examination: slitlamp examination showed conjunctival injection (abnormal) Slitlamp examination showed conjunctival injection, trace anterior chamber cells. On an unknown date, Visual acuity tests: bcva was 20/25 in each eye BCVA was 20/25 in each eye, decreased BCVA was reduced to 20/50 in the involved eye and normal Within 3 weeks, BCVA in the left eye recovered to 20/30 with resolution of anterior chamber cells.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered CORNEAL GRAFT REJECTION (Acute Corneal Transplant Rejection) and VISUAL IMPAIRMENT (declining vision in the left eye) to be possibly related.    This case concern 3 out of 4 patients.  This case concerns a 69-year-old, female patient with medical history of type 2 diabetes mellitus and non progressive Salzmann nodular degeneration in the left eye had received Descemet membrane endothelial keratoplasty in both eyes 6 years ago for Fuchs endothelial corneal dystrophy, 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 2 weeks after the second dose of mRNA-1273 (Moderna COVID-19 vaccine; according to narrative, with administration date unknown). Slitlamp examination showed conjunctival injection, trace anterior chamber cells, and corneal stromal edema; Visual acuity tests; Best corrected visual acuity( BCVA) was 20/25 in each eye; After second dose of vaccine BCVA was was reduced to 20/50 in the involved eye; Visual acuity tests; normal; Within 3 weeks, BCVA in the left eye recovered to 20/30 with resolution of anterior chamber cells. The rechallenge was not applicable since the event occurred after the second dose and no additional dosing is expected. The event was considered related to the vaccine per the reporter's assessment. The medical history of type 2 diabetes mellitus remain as potential confounder for the event of visual impairment. The medical history of Descemet membrane endothelial keratoplasty and the time since graft placement (70% corneal transplants fail within 10 years despite local or systemic immunosuppressive therapy, also most rejections occurring one year after surgery, coinciding with latency in this case), could be potential confounders to corneal graft rejection. The benefit-risk relationship of the vaccine is not affected by this report.   This case was linked to MOD-2021-349123, MOD-2021-353542, MOD-2021-353543 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 13-Oct-2021: Follow up received by safety 14-Oct-2021 contains  new information about patient identifiers.; Sender's Comments: This case concerns a 69-year-old, female patient with medical history of type 2 diabetes mellitus and non progressive Salzmann nodular degeneration in the left eye had received Descemet membrane endothelial keratoplasty in both eyes 6 years ago for Fuchs endothelial corneal dystrophy, 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 2 weeks after the second dose of mRNA-1273 (Moderna COVID-19 vaccine; according to narrative, with administration date unknown). Slitlamp examination showed conjunctival injection, trace anterior chamber cells, and corneal stromal edema; Visual acuity tests; Best corrected visual acuity( BCVA) was 20/25 in each eye; After second dose of vaccine BCVA was was reduced to 20/50 in the involved eye; Visual acuity tests; normal; Within 3 weeks, BCVA in the left eye recovered to 20/30 with resolution of anterior chamber cells. The rechallenge was not applicable since the event occurred after the second dose and no additional dosing is expected. The event was considered related to the vaccine per the reporter's assessment. The medical history of type 2 diabetes mellitus remain as potential confounder for the event of visual impairment. The medical history of Descemet membrane endothelial keratoplasty and the time since graft placement (70% corneal transplants fail within 10 years despite local or systemic immunosuppressive therapy, also most rejections occurring one year after surgery, coinciding with latency in this case), could be potential confounders to corneal graft rejection. The benefit-risk relationship of the vaccine is not affected by this report.