COVID-19; Generally unwell; Feeling more tired; Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine; Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine; This spontaneous case was reported by a patient and describes the occurrence of COVID-19 (COVID-19), MALAISE (Generally unwell), FATIGUE (Feeling more tired), INTERCHANGE OF VACCINE PRODUCTS (Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine) and COVID-19 IMMUNISATION (Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine) in a patient of an unknown age and gender who received mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (batch no. 3030342) for COVID-19 prophylaxis.     Patient remained very inactive and fatigues. Any activity or walking has fatigued him. Social activity or vigorous tasking fatigued him for over a year.  The patient's past medical history included Fatigue extreme (Developed extreme fatigue attributed to extreme over exertion that was totally unfamiliar.) in February 2022, Thrombus (Resolved in 3 weeks with treatment.) on 09-Jun-2022, EKG (Normal results), Holter monitoring (Normal results), Echocardiogram (Normal results), MRI (Normal results), CXR (Normal results), SARS-CoV-2 IgG antibody test (He had COVID at some point) on 23-May-2022 and Vitamin D (Low. Supplement was started and back to normal.) on 23-Mar-2022. Previously administered products included for COVID-19 vaccination: Pfizer (Intramuscular, Arm, Lot no: EN6200, Dose 1) on 28-Feb-2021, Pfizer (Intramuscular, Arm, Lot no: EP7534, Dose 2) on 23-Mar-2021, Pfizer (Intramuscular, Arm, Lot no: FF2587 and Dose 3) on 31-Mar-2022. Past adverse reactions to the above products included No adverse effect with Pfizer, Pfizer and Pfizer. Concurrent medical conditions included GERD, Anxiety and Panic disorder. Concomitant products included SERTRALINE HYDROCHLORIDE (ZOLOFT) for Anxiety, CLONAZEPAM for Anxiety and Panic disorder, OMEPRAZOLE for GERD.    On 20-Sep-2023 at 10:30 AM, the patient received fourth dose of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (Intramuscular use) 1 dosage form. On 20-Sep-2023, the patient experienced INTERCHANGE OF VACCINE PRODUCTS (Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine) and COVID-19 IMMUNISATION (Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine). On 03-Oct-2023,  after starting mRNA-1273.815 (SPIKEVAX 2023-2024 PFS), the patient experienced MALAISE (Generally unwell) and FATIGUE (Feeling more tired). On 05-Oct-2023, the patient experienced COVID-19 (COVID-19). The patient was treated with MESTRANOL, NORETYNODREL (ENOVID) (nasal use) from 01-Oct-2023 to 03-Oct-2023 at a dose of UNK, tid, Nasal spray and NIRMATRELVIR, RITONAVIR (PAXLOVID) in October 2023 at a dose of UNK, bid. On 08-Oct-2023, MALAISE (Generally unwell) had resolved. At the time of the report, COVID-19 (COVID-19) and FATIGUE (Feeling more tired) was resolving and INTERCHANGE OF VACCINE PRODUCTS (Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine) and COVID-19 IMMUNISATION (Patient used Spikevax 2023-2024 formula following pfizer covid-19 vaccine) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 05-Oct-2023, SARS-CoV-2 test: Positive.         Patient received original vaccination for COVID in 2021. When fatigue continued patient had multiple heart tests. Patient felt a lot better by 07-Oct-2023 and seemed totally well by 08-Oct-2023. Since then fatigue again but not so bad. Overall patient felt like finally getting well from long COVID. Patient reported Paxlovid as wonder drug. Within 3 days of Paxlovid all symptoms were gone including apparent long COVID symptoms. They returned back with less severity.  Patient wished to receive Pfizer Booster but as Moderna only available, patient received it.