he did not eat anything, he was not hungry; he slept most of the day; irrational; no recollection of those two days almost 48 hours; This spontaneous case was reported by a patient family member or friend and describes the occurrence of DECREASED APPETITE (he did not eat anything, he was not hungry), HYPERSOMNIA (he slept most of the day), THINKING ABNORMAL (irrational) and MEMORY IMPAIRMENT (no recollection of those two days almost 48 hours) in a 79-year-old male patient who received mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (batch no. 3030498) for COVID-19 prophylaxis.    Co-suspect product included non-company product INFLUENZA VACCINE (INFLUENZA) for an unknown indication.    The patient had received other vaccines in the 4 weeks prior to COVID-19 vaccine.  The patient's past medical history included Knee replacement (he got a new knee). Previously administered products included for Product used for unknown indication: Pfizer (Patient had Pfizer previously). Past adverse reactions to the above products included Sleep walking with Pfizer. Concurrent medical conditions included Hypertension (Patient take Micardis for his blood pressure), Thyroid disorder (Patient take thyroid medicine) and Hypercholesterolemia (Patient take cholesterol medication). Concomitant products included TELMISARTAN (MICARDIS) for Hypertension.   On 18-Oct-2023, the patient received dose of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (unknown route) 1 dosage form and dose of INFLUENZA VACCINE (INFLUENZA) (unknown route) 1 dosage form. On 18-Oct-2023, the patient experienced MEMORY IMPAIRMENT (no recollection of those two days almost 48 hours). On 19-Oct-2023, the patient experienced DECREASED APPETITE (he did not eat anything, he was not hungry), HYPERSOMNIA (he slept most of the day) and THINKING ABNORMAL (irrational). On 20-Oct-2023, THINKING ABNORMAL (irrational) and MEMORY IMPAIRMENT (no recollection of those two days almost 48 hours) had resolved. At the time of the report, DECREASED APPETITE (he did not eat anything, he was not hungry) and HYPERSOMNIA (he slept most of the day) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In October 2023, Heart rate: 99 and normal again down to 77  after about 36 hours. On 18-Oct-2023, Heart rate: 105. On an unknown date, Heart rate: usually around 70 to 72.         The dosage text was reported as unknown. The patient got the new Moderna booster. The patient had no recollection of anything the rest of the day on that day. Next day the patient slept most of the day and woke up saying things that were irrational. The patient had no recollection of those two days almost 48 hours. The patient was so out of it, did not eat anything and was not hungry. Scary thing was the patient got up to get his car keys. It was a very frightening experience. No treatment medication was reported.  Company Comment: This spontaneous case concerns a 79-year-old male patient with medical history of past adverse reactions wit Pfizer COVID-19 vaccine including Sleep walking, who experienced the unexpected, non-serious, AESI of Hypersomnia, 1 day after a dose of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS). It was reported that patient had no recollection of anything the rest of the day on that day. Next day the patient slept most of the day and woke up saying things that were irrational. The patient had no recollection of those two days almost 48 hours. The patient did not eat anything and was not hungry. The patient got up to get his car keys. Patient has had the same reaction with Pfizer vaccines which he had previously. This time with Moderna was worst with 48 hours of being totally out of it. With Pfizer, he had sleepwalking, wandering around but it did not last very long. Usually the patient's heart rate was around 70 to 72. Caller took his pulse the first day he got the vaccine, and it was around 105, one time it was up to 99. He was sleeping all day off and on. But it was back down normal again down to 77 pulse rate after about 36 hours. No further clinical information was provided for review. The reported medical history could be associated with the event. The concomitant Influenza Vaccine given on the same date as the vaccine could also be a confounder for the event. The benefit-risk relationship of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) vaccine is not affected by this report.