Recombinant Hepatitis B Vaccine (Engerix-B??)

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Abstract
Engerix-B® (Hep-B[Eng]) is a noninfectious recombinant DNA vaccine containing hepatitis B surface antigen (HBsAg). It is produced from genetically engineered yeast (Saccharomyces cerevisiae). Intramuscular Hep-B(Eng) [0-, 1-, 6-month schedule] has excellent immunogenicity in healthy neonates and infants, children, adolescents and adults, with seroprotection rates of 85–100% seen ≈1 month after the final dose of vaccine; seroprotection was defined as an antibody against HBsAg (anti-HBs) titre of ≥10 IU/L. The use of alternative Hep-B(Eng) immunisation schedules (e.g. a 0-, 1-, 2-, 12-month schedule in neonates and infants, 0-, 12-, 24-month or two-dose schedules in children and adolescents, and accelerated schedules in adults) have also been associated with high rates of seroprotection. Seroprotection rates were generally similar with Hep-B(Eng) and the recombinant vaccine Recombivax HB® (Hep-B[Rax]) or plasma-derived vaccines (PDVs)≈=1 month after the final dose (although anti-HBs geometric mean titres were significantly higher with Hep-B[Eng] than with Hep-B[Rax]). One month after the final dose, adults had significantly higher seroprotection rates with the recombinant triple-antigen vaccine Bio-Hep-B® (Hep-B[Bio]) than with Hep-B(Eng), although seroprotection rates in healthy infants were similar with Hep-B(Eng) and Hep-B(Bio). Hep-B(Eng) had excellent immunogenicity in several groups considered at high risk of acquiring hepatitis B (e.g. neonates born to hepatitis B carrier mothers and healthcare workers). The immunogenicity of Hep-B(Eng) was reduced in patients with conditions associated with impaired immune function (e.g. patients undergoing haemodialysis or being treated for malignancy), although it had good immunogenicity in patients with diabetes mellitus. Hep-B(Eng) had excellent protective efficacy against HBsAg carriage in healthy infants and children, and in neonates born to hepatitis B carrier mothers (protective efficacy of 95–99%). Hep-B(Eng) also demonstrated good protective efficacy in a number of other high-risk groups. Hep-B(Eng) is generally well tolerated with a tolerability profile similar to that of Hep-B(Rax), Hep-B(Bio) and PDVs. In conclusion, Hep-B(Eng) is a well established, highly immunogenic hepatitis B vaccine with good tolerability and excellent protective efficacy; it offers flexibility through a variety of immunisation schedules. In addition, it appears that Hep-B(Eng) confers immunity for at least 10 years. Hep-B(Eng) has an important role in mass vaccination campaigns against hepatitis B, as well as in groups considered at high risk of acquiring hepatitis B. The immunogenicity of the recombinant hepatitis B vaccine Engerix-B® (Hep-B[Eng]) has been examined in numerous studies; only the results of larger, fully published studies are discussed. Hep-B(Eng) was administered intramuscularly unless stated otherwise. Seroprotection is defined as an antibody against hepatitis B surface antigen (HBsAg) [anti-HBs] titre of ≥10 IU/L. Immune Response in Healthy Neonates and Infants Administration of Hep-B(Eng) 10µg (0-, 1-, 6-month schedule) results in high seroprotection rates in healthy neonates and infants. Approximately 1 month after the final dose of vaccine, seroprotection rates were 92.6–100% and anti-HBs geometric mean titres (GMTs) were 85–3210.9 IU/L. Recipients of the recombinant triple-antigen vaccine Bio-Hep-B® (Hep-B[Bio]) achieved seroprotection more rapidly than Hep-B(Eng) recipients. However, 1 month after the third dose of vaccine, seroprotection rates were similar with the recombinant hepatitis B vaccines Hep-B(Eng), Hep-B(Bio), Hepavax Gene® and GenHevac B® (87–100%). Hep-B(Eng) does not appear to be less immunogenic in preterm than in term neonates. Healthy infants achieved seroprotection more rapidly with Hep-B(Eng) than with the recombinant single-antigen vaccine Recombivax HB® (Hep-B[Rax]) using an alternative 2-, 4-, 6-month schedule. Anti-HBs GMTs were significantly higher with Hep-B(Eng) than with Hep-B(Rax) at all timepoints following the second dose of vaccine. Concomitant administration of Hep-B(Eng) and other routine childhood vaccines (i.e. diphtheria, tetanus, pertussis [whole-cell or acellular] and/or oral poliovirus vaccines) resulted in high rates of seroprotection (76.5–99%) and similar anti-HBs titres to those seen in healthy infants who received Hep-B(Eng) alone. Moreover, concomitant administration of Hep-B(Eng) did not alter the immunogenicity of the other childhood vaccines. Immune Response in Older Children and Adolescents Hep-B(Eng) 10 or 20µg (0-, 1-, 6-month schedule) has excellent immunogenicity in children and adolescents, with seroprotection rates of 95–100% and anti-HBs GMTs of 690-10 316 IU/L seen 7 months after administration of the first dose of vaccine. Two studies in children and adolescents revealed similar seroprotection rates (98.0–99.2%) with Hep-B(Eng) or Hep-B(Rax). In both studies, anti-HBs GMTs were significantly higher after administration of Hep-B(Eng) than after administration of Hep-B(Rax). High rates of seroprotection can be achieved in adolescents using immunisation schedules other than the standard schedule. Similar seroprotection rates occurred in recipients of Hep-B(Eng) 10µg administered by a 0-, 1-, 6-month schedule or a 0-, 12-, 24-month schedule (99.5% vs 98.1%), although the anti-HBs GMT was significantly higher with the former schedule (5687.4 vs 3158.7 IU/L). Administration of Hep-B(Eng) 20µg via two-dose schedules (0-,4-month, 0-, 6-month or 0-, 12-month schedules) was associated with seroprotection rates of 93.4–97.9% and anti-HBs GMTs of 1386–4155 IU/L. Immune Response in Healthy Adults Hep-B(Eng) 20µg (0-, 1-, 6-month schedule) has good immunogenicity in healthy adults, with seroprotection rates of 85–100% and an anti-HBs GMT of 1812–22 601 IU/L 7 months after the first dose of vaccine. Following vaccination, seroprotection rates were similar in healthy adults who received Hep-B(Eng) 20µg or Hep-B(Rax) 10µg, although anti-HBs GMTs were significantly higher with Hep-B(Eng) than with Hep-B(Rax). Healthy adults receiving the triple-antigen vaccine Hep-B(Bio) achieved significantly higher seroprotection rates than Hep-B(Eng) recipients 1 month after the first and final doses of vaccine. One month after the final dose of vaccine, seroprotection rates and anti-HBs GMTs were similar in recipients of Hep-B(Eng) 20µg and the plasma-derived vaccine (PDV) Heptavax® (PDV-Hep). Administration of Hep-B(Eng) 20µg using an accelerated 0-, 1-, 2-, 12-month schedule was associated with seroprotection rates of 84–100% 3 months after the first dose. Thirteen to 48 months after the first vaccine dose, seroprotection rates were 94–100%. Using this schedule, seroprotection rates and anti-HBs GMTs were similar with Hep-B(Eng) 20µg and PDV-Hep 20µg. A seroprotection rate of 76.4% occurred 1 month after the last dose of a 0-, 7-, 21-day schedule; the seroprotection rate was ≈94% at month 7–8 and, following a booster dose at month 12, the seroprotection rate at month 13 was ≈99%. Immune Response in High-Risk Groups Neonatal vaccination with Hep-B(Eng) prevents the vertical transmission of hepatitis B virus (HBV) from women who are chronic hepatitis B carriers to their neonates. At 1 year of age, seroprotection rates of 94–100% and anti-HBs GMTs of 158–9699 IU/L were seen in infants who had received passive-active (hepatitis B immunoglobulin [HBIG] plus Hep-B[Eng]) or active (Hep-B[Eng] alone) immunisation (neonates received Hep-B[Eng] 10 or 20µg according to various schedules). The protection afforded by Hep-B(Eng) persisted for at least 10 years. Healthcare workers receiving Hep-B(Eng) 20µg at months 0, 1 and 6 had seroprotection rates of 86–100% (anti-HBs GMT of 4264–4931 IU/L) 7–9 months after the first dose. Hep-B(Eng) produced significantly higher seroprotection rates than Hep-B(Rax) and had similar efficacy to PDV. The results of a small double-blind study (n = 48) in healthcare workers indicate that a vaccination schedule started with Hep-B(Rax) can be completed with Hep-B(Eng). An accelerated schedule (Hep-B[Eng] 20µg at 0,1 and 2 months) was associated with a seroprotection rate of 96.9% (anti-HBs GMT of 346.7 IU/L). In patients undergoing haemodialysis who received Hep-B(Eng) 40µg at months 0, 1, 2 and 6, seroprotection rates were 77.5–80% 1 month after the last dose. Hep-B(Eng) produced low seroprotection rates in patients with malignancy who were receiving induction/consolidation chemotherapy (10.5% and 18.9%), although seroprotection rates were higher in patients receiving maintenance chemotherapy (32%) or patients who were in remission after the completion of chemotherapy (88%). Hep-B(Eng) also demonstrated good immunogenicity in inmates in a correctional facility, institutionalised individuals with intellectual impairment, patients with congenital clotting disorders and homosexual men (83–99%). However, lower seroprotection rates were attained in adults awaiting liver transplantation (16–44%) and in injecting drug users (43–76%). Immune Response in Patients with Concomitant Disease Hep-B(Eng) had good immunogenicity in patients with diabetes mellitus. Seroprotection rates were 93.9% in children and adolescents and 94.4–98.7% (anti-HBs GMT of 5041–5887 IU/L) in adults. Seroprotection rates with Hep-B(Eng) were significantly lower in patients with chronic hepatitis C than in healthy controls in two studies (63.6% vs 93.9% and 71.7% vs 92.3%), but not in a third (88.5% vs 91.4%). Alcoholics receiving Hep-B(Eng) 20µg (0-, 1-, 6-month schedule) had seroprotection rates of 62% and 46.2% 1 month and 24 weeks after the last dose of vaccine. A higher seroprotection rate (75% 24 weeks after the last dose) was achieved in patients who received Hep-B(Eng) 40µg at 0, 1,2 and 6 months. The immunogenicity of Hep-B(Eng) is reduced in adults, infants and children with HIV infection. Response appears to be linked to the degree of immune dysfunction; responders had higher CD4+ cell counts than nonresponders. Other Considerations Administration of ≥1 doses of Hep-B(Eng) was beneficial in healthy individuals who had a suboptimal response to prior hepatitis B vaccination. Several host factors have been shown to affect the immunogenicity of Hep-B(Eng). Following vaccination, seroprotection rates were lower in men than in women, in older compared with younger individuals, in smokers than in nonsmokers, in individuals with a higher compared with a lower body mass index and in individuals with certain concomitant diseases compared with otherwise healthy individuals. There is also a genetic basis to response as multiple genes within the major histocompatibility complex have been shown to modulate the response to Hep-B(Eng). Hep-B(Eng) had good protective efficacy against HBsAg carriage in healthy infants and children and in neonates born to hepatitis B carrier mothers (protective efficacy of 95–99%). In children who had been born to hepatitis B carrier mothers and had been vaccinated as neonates, silent or natural HBV infection occurred in 8–12% after 8–10 years' follow-up. Hep-B(Eng) also demonstrated good protective efficacy in homosexual men, institutionalised individuals with intellectual impairment, patients undergoing haemodialysis, injecting drug users and patients with haemophilia. Hep-B(Eng) had poor protective efficacy in patients with newly diagnosed acute lymphoblastic leukaemia receiving chemotherapy; 48.8% of patients were found to be HBsAg-positive. Modelling studies, conducted in a variety of countries (e.g. Spain, Italy, The Gambia, the UK, and the US and/or Canada), that examined the cost effectiveness of mass vaccination campaigns against hepatitis B generally concluded that mass vaccination of infants and/or adolescents is a cost-saving strategy. A recent review article suggests that although mass vaccination is cost saving in countries of low, intermediate and high endemicity, it is not clear if such a strategy is cost saving in countries of very low endemicity (e.g. the UK, Ireland, Scandinavia and Iceland). Mass adolescent immunisation was the most cost-effective strategy against hepatitis B in a Spanish modelling study specifically examining the use of Hep-B(Eng); the study examined mass adolescent immunisation, mass infant immunisation and combined (infant and adolescent) mass immunisation. Hep-B(Eng) is generally well tolerated. Approximately 50% of 7618 healthy adults who received Hep-B(Eng) in 60 clinical trials reported no adverse events. There was no apparent correlation between vaccine dose and reported adverse events, and the proportion of individuals reporting adverse events decreased with each subsequent dose of vaccine (from 53.7% after the first dose to 34.6% after the third dose). Approximately 94% of 1289 neonates and 87% of 2142 children who received Hep-B(Eng) in 13 clinical trials experienced no adverse events. Postmarketing surveillance data collated after the distribution of ≈500 million doses of Hep-B(Eng) found that injection site reactions, rash, fever, nausea and headache were the most frequent (3.06–4.92 per million doses) adverse events. Less frequent adverse events (0.65–2.78 per million doses) included malaise, fatigue, influenza-like symptoms, vomiting, dizziness, pruritus, arthralgia, myalgia, diarrhoea, urticaria, paraesthesia and somnolence. Although there have been reports of CNS demyelinating events in individuals receiving hepatitis B vaccines, recent studies indicate that hepatitis B vaccination is not associated with an increased risk of CNS demyelinating disorders or an increased risk of relapse in patients with multiple sclerosis. The tolerability profile of Hep-B(Eng) is similar to that of PDVs or other recombinant vaccines. Hep-B(Eng) was well tolerated when administered con-comitantly with other routine childhood vaccines in infants (vaccines were administered using different syringes at different sites). Hep-B(Eng) is indicated for active immunisation against infection caused by all known HBV subtypes. The vaccine is available as a 0.5 or 1mL suspension containing 10 or 20µg of HBsAg. Hep-B(Eng) should be administered intramuscularly in the deltoid region in adults and in the anterolateral thigh in neonates and infants; it may be administered subcutaneously in patients at increased risk of haemorrhage. In all age groups, the standard Hep-B(Eng) schedule comprises three doses at months 0, 1 and 6. The recommended Hep-B(Eng) dose is 10µg in infants and 20µg in adults. Adolescents should receive Hep-B(Eng) 10 or 20µg (dosage recommendations vary according to region). Patients undergoing haemodialysis should receive Hep-B(Eng) 40µg at months 0, 1, 2 and 6. An accelerated 0-, 1-, 2-, 12-month schedule confers more rapid protection and may allow infants to receive Hep-B(Eng) simultaneously with other childhood vaccines. This accelerated schedule is also an option for populations such as infants born to mothers who are hepatitis B carriers, travellers to high-risk areas and other individuals who have or who might have been recently exposed to HBV. Infants born to mothers who are hepatitis B carriers and other unprotected individuals recently exposed to HBV should receive HBIG in addition to Hep-B(Eng). In exceptional circumstances (e.g. in individuals who are travelling to an area of high endemicity and who start vaccination within 1 month prior to departure), EU prescribing information states that adults may receive Hep-B(Eng) according to a 0-, 7-, 21-day schedule (with a booster dose at 12 months). If booster vaccination is required, US prescribing information recommends a Hep-B(Eng) dose of 10µg in individuals aged≤10 years and 20µg for individuals aged ≥11 years. The use of Hep-B(Eng) is contraindicated in individuals with hypersensitivity to any component of the vaccine and appropriate medical treatment should be available at the time of administration in the rare case of anaphylaxis.