Bad case of Covid-19; 2 Moderna, 1 Pfizer, 2 Novavax vaccines; Bad case of Covid-19; Significantly ill; Cough; Oxygen saturation went down; about 88; Pain in right arm; right shoulder never did recover; 2 Moderna, 1 Pfizer, 2 Novavax vaccines (2 booster doses); Myalgias, muscle aches, through my entire body, it was hard to roll over in bed; Fever; This serious initial spontaneous safety report was received by Novavax on 22-AUG-2023 from a consumer and a pharmacist, via the contact center.  A White (Caucasian) male of 75 year-old was vaccinated with intramuscular use Novavax Covid-19 Vaccine, Adjuvanted 10 ug/mL suspect Covid-19 vaccine dose 4 on 10-AUG-2022 and dose 5 on 31-AUG-2022, in the left arm at a dentist office.  The individual's medical history included Benign prostatic hyperplasia, Gastrooesophageal reflux disease, Gout, Hypertension and Insulin-requiring type 2 diabetes mellitus, trovafloxacin drug allergy, and use of Demerol (pethidine hydrochloride), which resulted in nausea. Additionally, he received Moderna COVID-19 vaccine (elasomeran) dose 1 on 08-FEB-2021, which resulted in "Very little problems" including pain in arm, Moderna COVID-19 vaccine dose 2 on 08-MAR-2021, which resulted in problems with confusion and disorientation as to where the individual was at, paranoia, insomnia, illogical thinking, and brain fog, and Pfizer BioNTech COVID-19 vaccine (tozinameran) dose 3 (booster) on SEP-2021 (two different dates were mentioned by reporter), which resulted in "some cognitive problems," brain fog, forgetfulness, and disorientation.    The following concomitant medications were reported: insulin, metformin, Trulicity (dulaglutide), ramipril, lansoprazole, allopurinol and tadalafil.  On 10-AUG-2022, the individual received their first dose of Novavax Covid-19 Vaccine dose 4 following 2 doses of Moderna COVID-19 vaccine and 1 dose of Pfizer BioNTech COVID-19 vaccine (PT: COVID-19 immunisation) (PT: Off label use) (PT: Vaccination failure) (Serious: Medically Significant). On 05-MAR-2023, the individual tested positive for COVID-19 via provided, at home PCR test (PT: Breakthrough COVID-19).  On unspecified date(s) in MAR-2022, he was significantly ill (PT: Illness), and he tested positive more than once (specific number of tests was not reported). The individual experienced myalgias, muscle aches, through his entire body, making it hard to roll over in bed (PT: Myalgia). The myalgia started in his arms near his shoulders, and the left shoulder recovered completely, but the individual's right shoulder never did recover and he was having a lot of difficulty functioning because of pain in right arm (PT: Pain in extremity). In MAR-2023, shortly after the myalgia began, he experienced cough (PT: Cough) and fever (PT: Pyrexia). His oxygen saturation went down to a point where he was a little nervous. It went down to about 88, and reported normal was like 97, 98 (PT: Oxygen saturation decreased). The individual did not go to the hospital due to the event, and for treatment he took high doses of zinc. Additionally, on 22-AUG-2023, the individual had his right shoulder injected with local anesthetic and steroids, after seeing an orthopedic doctor, which subsequently caused issues with his pre-existing condition, diabetes mellitus.    Relevant lab tests included: Oxygen saturation (Result: 88 (units not reported); MAR-2023) and SARS-CoV-2 test (Result: Positive; 05-MAR-2023 and multiple positive tests on unspecified dates.)  On 10-AUG-2022, the event outcome of Vaccination failure was recovered/resolved. On 31-AUG-2022, COVID-19 immunisation and Off label use were recovered/resolved. On unspecified date(s) in 2023, Breakthrough COVID-19, Illness, Cough, Pyrexia and Oxygen saturation decreased were recovered/resolved and Myalgia and Pain in extremity were recovering/resolving.  Discrepancies were identified in the source documents as follows: The dates of administration for Moderna COVID-19 vaccine were reported as 2021 and 2023, confirmation was obtained the vaccinations were administered in 2021, and subsequently captured accordingly. The dates of administration for Pfizer COVID-19 vaccine were reported as 03-SEP-2021 and 23-SEP-2021, therefore were captured in the structured fields as an unknown date in SEP-2021. Also, the batch/lot number for dose 4 was reported in part but the last number was illegible, therefore it was not captured in the structured field.; Sender's Comments: This 75 year-old male experienced: Vaccination failure, COVID-19 immunisation, Off label use, Breakthrough COVID-19, Cough, Illness, Myalgia, Oxygen saturation decreased, Pain in extremity and Pyrexia after vaccination with Novavax Covid-19 Vaccine, Adjuvanted 10 ug/mL. The event Vaccination failure was assessed as serious. The events COVID-19 immunisation, Off label use, Breakthrough COVID-19, Cough, Illness, Myalgia, Oxygen saturation decreased, Pain in extremity and Pyrexia were reported as non-serious. Based on the spontaneous nature of the report, the causal relationship between Novavax Covid-19 Vaccine, Adjuvanted and the reported event of vaccination failure is considered Related and between Novavax Covid-19 Vaccine, Adjuvanted and the other reported events is considered Possible.