Covid-19; This spontaneous case was reported by a physician and describes the occurrence of COVID-19 (Covid-19) in a 75-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 026121b) for COVID-19 vaccination.     The patient had no drug allergy. The patient had previously received a COVID-19 vaccine.     On 01-Apr-2022 at 12:15 PM, the patient received fourth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced COVID-19 (Covid-19). The patient was treated with NIRMATRELVIR, RITONAVIR (PAXLOVID) (oral) from 30-Apr-2022 to 04-May-2022 for COVID-19 treatment, at an unspecified dose and frequency. At the time of the report, COVID-19 (Covid-19) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 05-May-2022, SARS-CoV-2 test: negative negative antigen test on day 5. On 09-May-2022, SARS-CoV-2 test: positive very strong positive antigen test on day 9.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Concomitant medications were not reported.  The patient was not taking other medications/products within 2 weeks of starting COVID-19 treatment.  The patient  had tested negative via antigen test on day five when the symptoms also got resolved, but then the URI (upper respiratory infection) symptoms started again since 09-May-2022.  The device date was reported as 10-May-2022.  Company comment-This spontaneous case concerns a 75-year-old female patient with no medical history reported, who experienced the unexpected non serious AESI of Covid 19 infection on an unknown date after receiving the 4th dose of mRNA-1273 vaccine in the covid 19 vaccination series. It was reported that the patient was treated with paxlovid starting on 30-April-2022 for covid 19 treatment for 5 days. Details of the onset date, lab results and symptoms of this initial Covid 19 infection and its outcome was not reported. Patient had rebound covid, five days after completion of paxlovid with negative antigen test, followed by URI symptoms and very strong positive antigen test on day nine. The current pandemic situation of COVID 19 may remain as confounder and elderly age remains a risk factor to the event Covid-19.  The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report. Event seriousness assessed per medical judgement.; Sender's Comments: This spontaneous case concerns a 75-year-old female patient with no medical history reported, who experienced the unexpected non serious AESI of Covid 19 infection on an unknown date after receiving the 4th dose of mRNA-1273 vaccine in the covid 19 vaccination series. It was reported that the patient was treated with paxlovid starting on 30-April-2022 for covid 19 treatment for 5 days. Details of the onset date, lab results and symptoms of this initial Covid 19 infection and its outcome was not reported. Patient had rebound covid, five days after completion of paxlovid with negative antigen test, followed by URI symptoms and very strong positive antigen test on day nine. The current pandemic situation of COVID 19 may remain as confounder and elderly age remains a risk factor to the event Covid-19.  The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report. Event seriousness assessed per medical judgement.