A 20-y-old male presented with symptoms of meningococcal sepsis and died despite appropriate medical interventions. Blood cultures grew N. meningitidis serogroup Y. The patient had received the meningococcal quadrivalent (A,C,W-135,Y) polysaccharide vaccine 15 mo previously. Because the patient had a history of meningococcal meningitis at age 10, archived serum was obtained for further analysis. Complement component C7 was found to be deficient, and antibody levels to meningococcal polysaccharides were undetectable for two serogroups and low for the infecting serogroup 10 mo post-vaccination. This case highlights the fact that some individuals with terminal complement component deficiencies mount an impaired or short-lived response to vaccination with meningococcal capsular polysaccharides, and underscores the appropriateness of a more aggressive vaccination strategy in this patient population.