Rebound of Covid symptoms; This spontaneous case was reported by a patient and describes the occurrence of COVID-19 (Rebound of Covid symptoms) in a 33-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.    Co-suspect product included non-company product TOZINAMERAN (PFIZER BIONTECH COVID-19 VACCINE) for an unknown indication.    Patient previously had received a COVID-19 Vaccine.  Concurrent medical conditions included Type 1 diabetes mellitus (type 1 for 29 years, well controlled). Concomitant products included INSULIN LISPRO (HUMALOG) for an unknown indication.   On 29-Apr-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 07-Nov-2021, the patient received third dose of TOZINAMERAN (PFIZER BIONTECH COVID-19 VACCINE) (unknown route) 1 dosage form. On an unknown date, the patient experienced COVID-19 (Rebound of Covid symptoms). At the time of the report, COVID-19 (Rebound of Covid symptoms) was resolving.            Patient's race was reported.  It was reported that the patient was taking any other medications/products within 2 weeks of starting COVID-19 treatment.  Rebound of COVID symptoms occurred on 27-May-2022 at 08:00.   Patient received unspecified medication for the treatment of Covid-19 from 18-May-2022 to 23-May-2022. The device date reported as 28-May-2022.  Company Comment: This is a spontaneous case concerning a 33-year-old, male patient with no relevant medical history and with vaccine history of receiving Covid-19 BioNTech as the third dose of Covid-19 vaccine, who experienced the unexpected non-serious AESI event of Covid-19. The event occurred approximately 12-13 months after the second dose of mRNA-1273 vaccine administration, in Covid-19 vaccination in series. The event was described as, approximately 384 days after the second dose of mRNA-1273 vaccine administration, patient took unspecified medication for treatment of Covid-19. Approximately 4 days after the last dose of unspecified medication for treatment of Covid-19, patient experienced rebound of Covid-19 symptoms. No other information surrounding the event was reported. The outcome of the event was reported as resolving. The current Covid-19 pandemic remain confounder for the event. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 02-Jun-2022: Follow-up received non significant information manufacturer report number added.; Sender's Comments: This is a spontaneous case concerning a 33-year-old, male patient with no relevant medical history and with vaccine history of receiving Covid-19 BioNTech as the third dose of Covid-19 vaccine, who experienced the unexpected non-serious AESI event of Covid-19. The event occurred approximately 12-13 months after the second dose of mRNA-1273 vaccine administration, in Covid-19 vaccination in series. The event was described as, approximately 384 days after the second dose of mRNA-1273 vaccine administration, patient took unspecified medication for treatment of Covid-19. Approximately 4 days after the last dose of unspecified medication for treatment of Covid-19, patient experienced rebound of Covid-19 symptoms. No other information surrounding the event was reported. The outcome of the event was reported as resolving. The current Covid-19 pandemic remain confounder for the event. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.