This case was reported in a literature article and described the occurrence of unknown cause of death in a adult subject who received Hepatitis B vaccine. On an unknown date, unknown after receiving Hepatitis B vaccine, the subject developed unknown cause of death. Serious criteria included death and GSK medically significant. The outcome of unknown cause of death was fatal. The reported cause of death was unknown cause of death. It was unknown if the investigator considered the unknown cause of death to be related to Hepatitis B vaccine. Additional information was provided. This case was reported in a literature and described death not otherwise specified (NOS) in a patient aged between 18 and 70 years of unspecified gender who was vaccinated with ENGERIX (GlaxoSmithKline). The patient was part of a post hoc analysis that compared the safety of HBsAg-1018 with ENGERIX-B, in 3 randomised, observer-blinded, active-controlled, multi-center phase 3 trials in adults. Eligible participants in HBV-10 and HBV-16 were generally healthy volunteers but HBV-23 did not specify that participants must be generally healthy. Subjects in all three pivotal trials were serum negative for HBsAg, anti-HBs, and anti-HBc; had no history of HBV infection; had no history of prior immunization with any hepatitis B vaccine; did not have human immunodeficiency virus infection; had no autoimmune disease; and were not pregnant. No information on patient's family history or concomitant medication was provided. On an unspecified date, the patient received ENGERIX intramuscularly (administration site unspecified, dosage unknown; batch number not provided). [In this study, ENGERIX-B (GlaxoSmithKline Biologicals) consists of 20 mcg of recombinant HBsAg combined with 0.5 mg of aluminum hydroxide adjuvant per 1.0 mL dose. Participants in the ENGERIX-B group received the Food and Drug Administration (FDA) approved regimen of intramuscular injections at weeks 0, 4, and 24]. The age at vaccination was not provided. On an unspecified date, and unknown period after vaccination, the patient died. It was reported that the patient died due to illicit or therapeutic drug overdose. It was unknown if an autopsy was performed. This case has been considered serious due to death. The authors commented "Most deaths occurred in participants with significant pre-existing disease, comorbidities, or contributory social circumstances. The only imbalance in causes of death between the vaccine groups was in deaths due to illicit or therapeutic drug overdose (HBsAg-1018: n: 6 HBsAg-Eng: n:1". The authors concluded "the safety profile of HBsAg-1018 is similar to that of ENGERIX-B with vaccine-associated adverse events limited to mild to moderate local and systemic post-injection reactions. There is no evidence for a causal association between HBsAg-1018 and autoimmune or cardiovascular events. Although current hepatitis B vaccines have addressed a medical need in infants and adolescents, there remains a large unmet need in adults. A two dose hepatitis B vaccine with an acceptable safety profile should provide improved seroprotection and a significant public health benefit to adults 18 years of age or older". This is 1 of the 4 valid cases reported in the same literature article.