Suspected vaccination failure; Neisseria meningitides, serogroup undetermined/Neisseria Meningitis; Headache; Nuchal rigidity; Photophobia; Leg swelling; Respiratory distress; Pneumonia; Cough; Fever; Malaise; Back pain; This case was reported in a literature article and described the occurrence of suspected vaccination failure in a 19-year-old male patient who received Men ACWY-CRM NVS (Meningococcal polysaccharide groups A, C, W-135, Y conjugate vaccine) for prophylaxis. On an unknown date, the patient received Meningococcal polysaccharide groups A, C, W-135, Y conjugate vaccine at an unknown dose. On an unknown date, unknown after receiving Meningococcal polysaccharide groups A, C, W-135, Y conjugate vaccine, the patient experienced vaccination failure (serious criteria hospitalization and GSK medically significant), neisseria meningitides meningitis (serious criteria hospitalization and GSK medically significant), headache (serious criteria hospitalization), nuchal rigidity (serious criteria hospitalization), photophobia (serious criteria hospitalization), swelling of legs (serious criteria hospitalization), respiratory distress (serious criteria hospitalization and GSK medically significant), pneumonia (serious criteria GSK medically significant), cough, fever, malaise and back pain. The patient was treated with levofloxacin. On an unknown date, the outcome of the vaccination failure was unknown and the outcome of the neisseria meningitides meningitis, headache, nuchal rigidity, photophobia, swelling of legs, respiratory distress, pneumonia, cough, fever, malaise and back pain were recovered/resolved.   The reporter considered the vaccination failure, neisseria meningitides meningitis, headache, nuchal rigidity, photophobia, swelling of legs, respiratory distress, pneumonia, cough, fever, malaise and back pain to be related to Meningococcal polysaccharide groups A, C, W-135, Y conjugate vaccine.  Additional details were reported as follows: This case was reported in a literature article and described the suspected vaccination failure in a 19-year-old male patient who was vaccinated with unspecified quadrivalent meningococcal conjugated vaccine (manufacturer unknown) for prophylaxis. This case corresponds patient (case-2) reported in this literature article. The patient was the male. Previously the patient was healthy with no prior significant infections or pneumonias. The patient was the recruit. No information on patient's family history or concomitant condition was provided.  On unspecified date, at the beginning of the training, the patient received unspecified quadrivalent meningococcal conjugated vaccine (administration route and site unspecified, dosage unknown; batch number not provided). The age of vaccination was not provided. On an unspecified date, less than a year after vaccination, the patient developed cough, fever, malaise, and back pain 2 months into training. The patient was initially diagnosed with pneumonia and received levofloxacin. Subsequently, the patient developed severe headache, nuchal rigidity, photophobia, leg swelling, and respiratory distress requiring intubation and intensive care unit admission. Cerebrospinal fluid PCR (polymerase chain reaction) detected Neisseria meningitides, serogroup undetermined. The patient had clinical and laboratory findings for neisseria meningitis and complement deficiency such as 13 U/mL (40-60 range), AH50 - less than 35% normal (reference more than 59%), C2-1.7 mg/dL (1.6-3.5),  C3 119 mg/dL (90-180), C4 21 mg/dL (10-40 range), C5 less than 2 mg/dL (7-20), C6 10.4 mg/dL (7.2-12.8), C8 56.8 mg/dL (10.7-24.9), C9  25 mg/dL (6-29), IgM, IgG, IgA Normal, Diphteria, tetanus toxoid, and Hib titers Protected, Pneumococcal titers 11/14 protective more than 1.3 mg/mL, Genetic testing C5 variants detected (1. C.55C more than T, (p.Gln19.)- pathogenic and 2. C.4288A more than G, (p.Thr1430Ala)-unknown significance). Immune testing showed a reduced CH50 and low C5. Genetic testing of the C5 gene showed a pathogenic variant, c.55C more than T, and a variant of unknown significance, c.4288A more than G. This case has been considered as suspected vaccination failure being full schedule, time to onset and confirmed lab serotype was unknown. This case has been considered as serious due to suspected vaccination failure and hospitalization. Treatment was unknown. On unspecified date, the patient recovered without long-term sequelae. The author commented, "Invasive meningococcal disease is a significant cause of morbidity and mortality and has been associated with complement deficiencies, particularly in the terminal pathway. Because vaccination has become widespread and population immunity to the virulent strains develop, complement deficiency should be suspected because these patients are more susceptible to the lower virulent strains. The complement system is a key player in innate immunity and a bridge between innate and adaptive immunity. Specific to meningococcus and other encapsulated bacteria, the terminal complement forms the membrane attack complex, which inserts into the outer layer of gram-negative organisms, causing cell lysis. Therefore, deficiencies in each of the terminal components C5-C9 have been reported and are associated with recurrent meningococcal disease". The author concluded, "Although patients with terminal complement component deficiency should be vaccinated to both the quadrivalent MenACWY and MenB vaccines, they will not be protected from other serotypes. Given the risk for recurrent and severe infection, identifying complement deficiency is critical for mitigating future infections and associated morbidity and mortality". This is 1 of the 2 valid cases reported in this literature article.      Lab Comments: On an unknown date, the patient underwent lab test. Genetic testing C5 variants detected (1. C.55C more than T, (p.Gln19.)- pathogenic and 2. C.4288A more than G, (p.Thr1430Ala)-unknown significance). Immune testing showed a reduced CH50 and low C5. Genetic testing of the C5 gene showed a pathogenic variant, c.55C more than T, and a variant of unknown significance, c.4288A more than G.