Severe COVID-19/breakthrough COVID-19; reduced SARS-CoV-2 vaccine efficacy; This literature-non-study case was reported in a literature article and describes the occurrence of COVID-19 (Severe COVID-19/breakthrough COVID-19) in a 51-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.   LITERATURE REFERENCE: Clinically significant COVID-19 following SARS-CoV-2 vaccination in kidney transplant recipients.     The patient's past medical history included Kidney transplant (6.5 years ago). Concurrent medical conditions included Diabetes mellitus, Hypertension and Immunosuppression. Concomitant products included TACROLIMUS, MYCOPHENOLATE MOFETIL (MYCOPHENOLATE) and PREDNISONE for Immunosuppression.   In 2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. In 2021, received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. In 2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced COVID-19 (Severe COVID-19/breakthrough COVID-19) (seriousness criterion hospitalization prolonged). On an unknown date, the patient experienced DRUG INEFFECTIVE (reduced SARS-CoV-2 vaccine efficacy). At the time of the report, COVID-19 (Severe COVID-19/breakthrough COVID-19) and DRUG INEFFECTIVE (reduced SARS-CoV-2 vaccine efficacy) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In 2021, Blood creatinine: 2.44 (High) 2.44 mg/dL. In 2021, Blood grouping: b (Inconclusive) B blood group. In 2021, Body mass index: 35.2 (Inconclusive) 35.kg/m2. In 2021, SARS-CoV-2 antibody test: negative (Negative) negative at 23rd day. In 2021, SARS-CoV-2 test: positive (Positive) positive, respiratory specimen collected =14 days after completing the primary vaccination series.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter considered COVID-19 (Severe COVID-19/breakthrough COVID-19) and DRUG INEFFECTIVE (reduced SARS-CoV-2 vaccine efficacy) to be possibly related.    It was suggested reduced SARS-CoV-2 vaccine efficacy in those vulnerable patient population, likely stemming from the use of maintenance immunosuppression.  This case was supplement recent reports that most transplant recipients did not develop a measurable antibody response to standard anti-SARS-CoV-2 mRNA vaccination schedules, although immunogenicity was higher once both doses are administered.  Was concluded that these findings underscore the urgent need to implement trials for the development of alternate effective vaccine dosing schedules for these patients.  Company Comment: For the event Lack of drug effect causality is not applicable. Causality for event Severe COVID-19/breakthrough is possible.   This case was linked to MOD-2021-282564 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 10-Aug-2021: Follow up received by safety 12-Aug-2021 included an Email received from team and does not contain any new information.; Sender's Comments: For the event Lack of drug effect causality is not applicable. Causality for event Severe COVID-19/breakthrough is possible.