Interchange of vaccine products; Paxlovid rebound; COVID-19; This spontaneous case was reported by a consumer and describes the occurrence of SARS-COV-2 TEST POSITIVE (COVID-19), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and THERAPEUTIC PRODUCT INEFFECTIVE (Paxlovid rebound) in a 54-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 005m21A) for COVID-19 vaccination.    Co-suspect product included non-company product NIRMATRELVIR, RITONAVIR (PAXLOVID) for COVID-19 treatment.    The patient's past medical history included COVID-19 (After taking Paxlovid for 5 days, patient tested negative 4 times in 6 days and had no symptoms. 7 days after last dose of paxlovid, patient had new symptoms and tested positive again.). Previously administered products included for Product used for unknown indication: Pfizer/ BioNtech (Dose number 1, Batch number- EL3249) on 19-Jan-2021, Pfizer/ BioNtech (Dose number 2, Batch number- Em9810, Location of injection- Right arm) on 09-Feb-2021, Pfizer/ BioNtech (Dose number 3, Batch number- FF2588 and Location of injection- Right arm) on 21-Sep-2021. Past adverse reactions to the above products included No adverse reaction with Pfizer/ BioNtech, Pfizer/ BioNtech and Pfizer/ BioNtech. Concomitant products included EMTRICITABINE, TENOFOVIR ALAFENAMIDE FUMARATE (DESCOVY) from 26-Jan-2022 to an unknown date, PANTOPRAZOLE and ROSUVASTATIN for an unknown indication.   On 25-Apr-2022, the patient received fourth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 30-Apr-2022, the patient started NIRMATRELVIR, RITONAVIR (PAXLOVID) (unknown route) at an unspecified dose. On 10-May-2022, the patient experienced SARS-COV-2 TEST POSITIVE (COVID-19). On an unknown date, the patient experienced INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and THERAPEUTIC PRODUCT INEFFECTIVE (Paxlovid rebound). At the time of the report, SARS-COV-2 TEST POSITIVE (COVID-19), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and THERAPEUTIC PRODUCT INEFFECTIVE (Paxlovid rebound) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, SARS-CoV-2 test: positive (Positive) 7 days after last dose of Paxlovid, patient had new symptoms and tested positive again. and negative (Negative) After taking Paxlovid for 5 days, patient tested negative 4 times in 6 days and had no symptoms..         Patient was taking medications within 2 weeks of starting COVID-19 treatment. Paxlovid rebound Device date- 12-May-2022.  Company comment: This spontaneous case concerns a 54 year old male patient with no reported medical history, who experienced the unexpected non serious AESI of SARS-CoV-2 test positive, about 15 days after receiving the fourth dose with mRNA-1273 vaccine in the COVID-19 vaccination series. Therapeutic product ineffective (reported as Paxlovid rebound) was also reported. The patient received the previous three doses with Pfizer vaccine, the last dose being given about 7 months prior to mRNA-1273 vaccine . Interchange of vaccine products was noted. It was reported that patient was on Paxlovid treatment for 5 days for COVID-19 infection. He tested negative for COVID-19,  4 times in 6 days and had no symptoms. About 7 days after his last dose of paxlovid, he developed new symptoms and tested positive for COVID-19 again. No further information on risk factors and co morbidities, details about emergence of new symptoms was available in the report. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This spontaneous case concerns a 54 year old male patient with no reported medical history, who experienced the unexpected non serious AESI of SARS-CoV-2 test positive, about 15 days after receiving the fourth dose with mRNA-1273 vaccine in the COVID-19 vaccination series. Therapeutic product ineffective (reported as Paxlovid rebound) was also reported. The patient received the previous three doses with Pfizer vaccine, the last dose being given about 7 months prior to mRNA-1273 vaccine . Interchange of vaccine products was noted. It was reported that patient was on Paxlovid treatment for 5 days for COVID-19 infection. He tested negative for COVID-19,  4 times in 6 days and had no symptoms. About 7 days after his last dose of paxlovid, he developed new symptoms and tested positive for COVID-19 again. No further information on risk factors and co morbidities, details about emergence of new symptoms was available in the report. The benefit-risk relationship of mRNA-1273 is not affected by this report.