covid-19 prior to Paxlovid treatment.; interchange of vaccine products; This spontaneous case was reported by an other health care professional and describes the occurrence of COVID-19 (covid-19 prior to Paxlovid treatment.) and INTERCHANGE OF VACCINE PRODUCTS (interchange of vaccine products) in a 42-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 002M21A) for COVID-19 vaccination.     Previously administered products included for Drug use for unknown indication: Pfizer BioNTech (Dose Number: 1 Batch/Lot No: EN6204) on 15-Mar-2021, Pfizer BioNTech (Dose Number: 2 Batch Lot No: ER8734) on 05-Apr-2021 and Pfizer BioNTech (Dose Number: 3 Batch/Lot No: FE3592 Location of injection: Arm Left) on 15-Oct-2021. Past adverse reactions to the above products included No adverse event with Pfizer BioNTech, Pfizer BioNTech and Pfizer BioNTech. Concurrent medical conditions included Ulcerative colitis and Penicillin allergy. Concomitant products included ADALIMUMAB (HUMIRA) for an unknown indication.    On 19-Apr-2022 at 12:30 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 prior to Paxlovid treatment.) and INTERCHANGE OF VACCINE PRODUCTS (interchange of vaccine products). The patient was treated with NIRMATRELVIR, RITONAVIR (PAXLOVID) from 23-May-2022 to 28-May-2022 for COVID-19 treatment, at an unspecified dose and frequency. At the time of the report, COVID-19 (covid-19 prior to Paxlovid treatment.) had resolved and INTERCHANGE OF VACCINE PRODUCTS (interchange of vaccine products) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 28-May-2022, SARS-CoV-2 test: negative (Negative) Negative. On 29-May-2022, SARS-CoV-2 test: negative (Negative) Negative. On 31-May-2022, SARS-CoV-2 test: negative (Negative) Negative. On 02-Jun-2022, SARS-CoV-2 test: positive (Positive) Positive.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Paxlovid rebound case  tested positive twice 2-Jun-22 after testing negative on 28-May- 22, 29-May-22, 31-May-22 Device Date: 03Jun2022  The patient took other medications or products within 2 weeks of starting COVID-19 treatment. The patient previously received a COVID-19 Vaccine.  Company Comment: This spontaneous case concerns a 42-year-old female patient with no relevant medical history reported, who experienced the unexpected non-serious AESI event of COVID-19 which occurred unspecified days after receiving the fourth dose of mRNA-1273 vaccine. It was reported Patient was treated with Paxlovid from 23 rd to 28 th May 2022 for Covid-19 and tested negative on next three consecutive days, however she had a rebound covid and tested positive on 02 June 2022. The current pandemic situation of COVID-19 may remain as confounder to the event Covid-19.  The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.; Sender's Comments: This spontaneous case concerns a 42-year-old female patient with no relevant medical history reported, who experienced the unexpected non-serious AESI event of COVID-19 which occurred unspecified days after receiving the fourth dose of mRNA-1273 vaccine. It was reported Patient was treated with Paxlovid from 23 rd to 28 th May 2022 for Covid-19 and tested negative on next three consecutive days, however she had a rebound covid and tested positive on 02 June 2022. The current pandemic situation of COVID-19 may remain as confounder to the event Covid-19.  The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.