Engerix-B Mechanism of Action

vaccine, hepatitis b




Full Prescribing Info
Pharmaco-therapeutic group: Hepatitis B vaccine. ATC code: J07BC01.
Pharmacology: Pharmacodynamics: Engerix-B induces specific humoral antibodies against HBsAg (anti-HBs antibodies). AntiHBs antibody concentrations ≥ 10 IU/l correlate with protection to HBV infection.
Protective efficacy: At risk groups: In field studies, a protective efficacy between 95% and 100% was demonstrated in neonates, children and adults at risk. A 95% protective efficacy was demonstrated in neonates of HBeAg positive mothers, immunised according to the 0, 1, 2 and 12 or 0, 1 and 6 schedules without the concomitant administration of HBIg at birth. However, simultaneous administration of HBIg and vaccine at birth increased the protective efficacy to 98%.
Twenty years after primary vaccination during infancy, subjects born to mothers who were HBV carriers, received a challenge dose of Engerix-B. One month later, at least 93% of subjects (N=75) mounted an anamnestic response demonstrating immune memory.
Healthy subjects: The table below summarizes seroprotection rates (i.e. percentages of subjects with anti-HBs antibody concentrations ≥ 10 IU/l) obtained in clinical studies with the different schedules mentioned under Dosage & Administration: See Table 1.

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The seroprotection rates (SP) obtained with the two different dosages and schedules licensed in subjects from 11 years up to and including 15 years of age were evaluated up to 66 months after the first dose of the primary vaccination and are presented in the Table as follows: See Table 2.

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These data show that a primary vaccination with Engerix-B vaccine induces circulating antiHBs antibodies that persist for at least 66 months. After having completed the primary course, at each time point there is no clinically significant difference in the seroprotection rates when comparing the 2 vaccine groups. Indeed, all subjects in both vaccine groups (including subjects with anti-HBs antibody concentrations < 10 IU/l) received a challenge dose 72 to 78 months after primary vaccination. One month after the challenge dose, all subjects mounted an anamnestic response to the challenge dose and were shown to be seroprotected (i.e. antiHBs antibody concentrations ≥ 10 IU/l). These data suggest that protection against hepatitis B may still be conferred through immune memory in all subjects who responded to primary vaccination but lost seroprotection level of anti-HBs antibodies.
Rechallenge in healthy subjects: Subjects (N=284) aged 12 to 13 years vaccinated during infancy with 3 doses of Engerix-B received a challenge dose. One month later, 98.9% of subjects were shown to be seroprotected.
Patients with renal insufficiency including patients undergoing haemodialysis: See Table 3.

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Patients with type II diabetes: See Table 4.

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Reduction in the incidence of hepatocellular carcinoma in children: A significant reduction in the incidence of hepatocellular carcinoma has been observed in children aged 6-14 years following a nationwide hepatitis B vaccination in Taiwan. There was a significant decline in the prevalence of hepatitis B antigen, the persistence of which is an essential factor in the development of hepatocellular carcinoma.
Toxicology: Pre-clinical Safety Data: Appropriate safety tests have been performed.
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