unlike us he did not contract Covid last December when we became sick\I was symptomatic infected my wife. Infected my daughter. her Boyfriend; No one else in the family had received a full dose for their booster.; This spontaneous case was reported by a physician and describes the occurrence of COVID-19 (unlike us he did not contract Covid last December when we became sick\I was symptomatic infected my wife. Infected my daughter. her Boyfriend) and ACCIDENTAL UNDERDOSE (No one else in the family had received a full dose for their booster.) in an adult male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.    Co-suspect product included non-company product NIRMATRELVIR, RITONAVIR (PAXLOVID) for COVID-19 prophylaxis.    Previously administered products included for COVID-19 prophylaxis: MODERNA COVID-19 VACCINE (dose 1), MODERNA COVID-19 VACCINE (dose 4), MODERNA COVID-19 VACCINE (dose 3) and MODERNA COVID-19 VACCINE (dose 2). Past adverse reactions to the above products included No adverse event with MODERNA COVID-19 VACCINE, MODERNA COVID-19 VACCINE, MODERNA COVID-19 VACCINE and MODERNA COVID-19 VACCINE.   On an unknown date, the patient received fifth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form and NIRMATRELVIR, RITONAVIR (PAXLOVID) (unknown route) at an unspecified dose. On an unknown date, the patient experienced COVID-19 (unlike us he did not contract Covid last December when we became sick\I was symptomatic infected my wife. Infected my daughter. her Boyfriend) and ACCIDENTAL UNDERDOSE (No one else in the family had received a full dose for their booster.). At the time of the report, COVID-19 (unlike us he did not contract Covid last December when we became sick\I was symptomatic infected my wife. Infected my daughter. her Boyfriend) and ACCIDENTAL UNDERDOSE (No one else in the family had received a full dose for their booster.) outcome was unknown.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   In Dec-2022, the patient husband got infected and ended up infecting the rest of my family. All the family was vaccinated and boosted. The patient and her husband were sick. The family was boosted around the same time, but received half dose for the booster, and nobody got seriously ill and sick. The patient took Paxlovid, the patient was recovered, and it was interesting because when my husband was trying to determine what the appropriate booster was, totally five of us were infected and vaccination records are not available at the time of the call.  All family members received the same number of doses of COVID-19 vaccine except for the caller who works as a HCP.  Patient received 5 or 6 doses of the Moderna COVID19 vaccine.  No concomitant and treatment medications were reported.   This case was linked to US-MODERNATX, INC.-MOD-2023-745748 (Linked Report).   Most recent FOLLOW-UP information incorporated above includes: On 17-Oct-2023: Live Follow-up received that contains significant information: Reporter, patient detail, event, and Refence Ids updated.; Sender's Comments:  US-MODERNATX, INC.-MOD-2023-745748:Master case (Father's or Reporter's case)