COVID-19; 2 pfizer vaccines (April and May 2021); This spontaneous case was reported by a patient and describes the occurrence of COVID-19 (COVID-19) and INTERCHANGE OF VACCINE PRODUCTS (2 pfizer vaccines (April and May 2021)) in a 56-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.     Previously administered products included for Product used for unknown indication: PFIZER BIONTECH COVID-19 VACCINE in April 2021 and PFIZER BIONTECH COVID-19 VACCINE in May 2021. Past adverse reactions to the above products included No adverse event with PFIZER BIONTECH COVID-19 VACCINE and PFIZER BIONTECH COVID-19 VACCINE. Concurrent medical conditions included Drug allergy (Unspecified drug).    On 04-Nov-2021 at 2:00 PM, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 04-Nov-2021, the patient experienced INTERCHANGE OF VACCINE PRODUCTS (2 pfizer vaccines (April and May 2021)). On an unknown date, the patient experienced COVID-19 (COVID-19). The patient was treated with NIRMATRELVIR, RITONAVIR (PAXLOVID) from 16-May-2022 to 20-May-2022 for COVID-19 treatment, at an unspecified dose and frequency. At the time of the report, COVID-19 (COVID-19) had not resolved and INTERCHANGE OF VACCINE PRODUCTS (2 pfizer vaccines (April and May 2021)) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 14-May-2022, SARS-CoV-2 test: positive (Positive) Positive. In May 2022, SARS-CoV-2 test: positive (Positive) Tested positive day 5 after completing treatment and positive (Positive) 11days after final dose-still testing positive.         The patient did not take any other medications/products within 2 weeks of starting COVID-19 treatment.  Paxlovid started on 16-May-2022 (2 days after symptoms and testing positive) completed meds in 20-May-2022 . Symptoms subsided by day 3 of treatment. 4 days after completion of treatment symptoms returned. Tested positive day 5 after completing treatment. 11days after final dose-still testing positive. Still have head congestion. Device Date reported as 31May2022 in narrative.  Company comment-This spontaneous case concerns a female patient aged 56 years with no relevant medical history reported, who experienced the unexpected non serious AESI of Covid 19 approximately 6 months 10 days after receiving the booster dose of mRNA-1273 vaccine in the covid 19 vaccination series. Patient started paxlovid for covid infection two days after testing covid positive and with symptoms. Completed the treatment for 5 days. Symptoms recurred 4 days after completion of treatment and was tested positive again. Patient has received initial schedule of vaccinations (dose 1and 2) with TOZINAMERAN (interchange of vaccine products) noted. The current pandemic situation of COVID 19 may remain as confounder. 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 female patient aged 56 years with no relevant medical history reported, who experienced the unexpected non serious AESI of Covid 19 approximately 6 months 10 days after receiving the booster dose of mRNA-1273 vaccine in the covid 19 vaccination series. Patient started paxlovid for covid infection two days after testing covid positive and with symptoms. Completed the treatment for 5 days. Symptoms recurred 4 days after completion of treatment and was tested positive again. Patient has received initial schedule of vaccinations (dose 1and 2) with TOZINAMERAN (interchange of vaccine products) noted. The current pandemic situation of COVID 19 may remain as confounder. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report. Event seriousness assessed per medical judgement.