the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis; the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis; This literature-non-study case was reported in a literature article and describes the occurrence of OPHTHALMIC HERPES SIMPLEX (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) and HERPES SIMPLEX REACTIVATION (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) in a 54-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.   LITERATURE REFERENCE.    The patient's past medical history included Ophthalmic herpes simplex (of the left eye).   On 25-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 23-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 30-Mar-2021, the patient experienced OPHTHALMIC HERPES SIMPLEX (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) (seriousness criterion medically significant) and HERPES SIMPLEX REACTIVATION (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) (seriousness criterion medically significant). The patient was treated with LOTEPREDNOL at a dose of UNK, tid; VALACYCLOVIR [VALACICLOVIR] (oral) at a dose of 1 gram once a day and GANCICLOVIR at an unspecified dose and frequency. At the time of the report, OPHTHALMIC HERPES SIMPLEX (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) and HERPES SIMPLEX REACTIVATION (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Slit-lamp examination: central corneal subepithelial infiltrates with surrounding stromal haze in the right eye and at 1-week follow-up, a dendritic staining pattern was seen.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered OPHTHALMIC HERPES SIMPLEX (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) and HERPES SIMPLEX REACTIVATION (the intense immunological reaction following mRNA-based COVID-19 vaccination may have reactivated keratitis) to have an unknown relationship.    The study was conducted for mRNA-1273 (Moderna) COVID-19 vaccinations from January to June of 2021, and presented with symptoms of keratitis within 14 days. The patient developed pain in her right eye which started 1 week after receiving her second dose of the Moderna COVID-19 vaccination. Slit-lamp examination of the cornea revealed four subepithelial infiltrates inferotemporal to the visual axis with a mild stromal haze. The patient was prescribed loteprednol three times daily and valacyclovir 1 g by mouth daily. At 1-week follow-up, a dendritic staining pattern was seen. Ganciclovir was added to the treatment. Over the course of the following month, the patient showed significant improvement in her symptoms and presenting signs. The authors stated that immunological reaction following mRNA-based COVID-19 vaccinations may trigger new-onset or reactivation of keratitis. In addition, since the intense immunological reaction following COVID-19 vaccination increases levels of the cytokines, the authors hypothesized that it may trigger or reactivate a keratitis infection in these patients. Although more patients reported symptoms after their first dose, a faster onset was observed after patients received their second dose (10.5 days vs 4.4 days, respectively). This observation could be explained by the 30-fold stronger immune response following the second vaccine dose. Author stated that it was crucial to note that it have made only temporal associations, and causality cannot be determined. It was believed that  that the immunological response following COVID-19 vaccination may explain that phenomenon, though causality cannot be proven.   This case was linked to US-MODERNATX, INC.-MOD-2022-674613, US-MODERNATX, INC.-MOD-2022-674614, US-MODERNATX, INC.-MOD-2022-674525 (E2B Linked Report).  This literature-non-study case report concerns a 54-year-old female patient with medical history of herpes simplex virus of the left eye, who experienced serious (medically significant) unexpected events of Ophthalmic herpes simplex and Herpes simplex reactivation. Reportedly, 7 days after the patient had received the second dose of the mRNA-1273 vaccine, she developed pain in her right eye. Slit-lamp examination of the cornea revealed four subepithelial infiltrates inferotemporal to the visual axis with a mild stromal haze. The patient was prescribed loteprednol three times daily and valacyclovir 1 g by mouth daily. At 1-week follow-up, a dendritic staining pattern was seen. Ganciclovir was added to the treatment and over the course of the following month, the patient showed significant improvement in her symptoms and presenting signs. The authors concluded that immunological reaction following vaccination might trigger reactivation of keratitis in this patient, having in mind medical history of previous ophthalmic herpes simplex in the left eye. Previous medical history of ophthalmic herpes simplex infection remains a confounder. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This literature-non-study case report concerns a 54-year-old female patient with medical history of herpes simplex virus of the left eye, who experienced serious (medically significant) unexpected events of Ophthalmic herpes simplex and Herpes simplex reactivation. Reportedly, 7 days after the patient had received the second dose of the mRNA-1273 vaccine, she developed pain in her right eye. Slit-lamp examination of the cornea revealed four subepithelial infiltrates inferotemporal to the visual axis with a mild stromal haze. The patient was prescribed loteprednol three times daily and valacyclovir 1 g by mouth daily. At 1-week follow-up, a dendritic staining pattern was seen. Ganciclovir was added to the treatment and over the course of the following month, the patient showed significant improvement in her symptoms and presenting signs. The authors concluded that immunological reaction following vaccination might trigger reactivation of keratitis in this patient, having in mind medical history of previous ophthalmic herpes simplex in the left eye. Previous medical history of ophthalmic herpes simplex infection remains a confounder. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. US-MODERNATX, INC.-MOD-2022-674613:30 YO female US-MODERNATX, INC.-MOD-2022-674614:84 YO female US-MODERNATX, INC.-MOD-2022-674525:73 YO male